You'd think celebrities would know better.
In the era of viral video, a tirade in front of an open mic, an illicit tryst captured on a security camera or even a desperate voice mail left for a loved one all stand a good chance of ending up on the Internet and being seen or heard by millions around the world.
In some cases, celebrities used video to reach their fans directly. In other cases, a private moment captured on tape is made public.
Either way, here are the top nine celebrities caught on tape in 2009:
Christian BaleChristian Bale wasn't acting when he produced one of the most memorable moments on tape this year.
A recording of the "Dark Knight" star's four-minute F-word-laced tirade on the set of "Terminator Salvation" surfaced on the Internet in February.
The actor was shooting a scene with actress Bryce Dallas Howard when Shane Hurlbut, the film's director of photography, accidentally walked on the set, touching off the maelstrom.
Bale went ballistic, threatening to kick Hurlbut's "a--" and even get him fired. "I want you off the f---ing set, you p----," he shouted at Hurlbut.
When Hurlbut apologized, Bale brushed it off with, "No, don't just be sorry. Think for one f---ing second. ... Am I going to walk around and rip your f---ing lights down in the middle of the scene? ... Do you have any f---ing idea about it's f---ing distracting? Give me a f---ing answer."
Bale's rant took place a few days after his arrest in London in July 2008, when he was questioned and released by police after his mother, Jenny, and sister, Sharon, lodged a complaint against him. No charges were ever filed.
It will go down in history as one of the strangest television interviews ever.
Joaquin Phoenix's bearded, bloated appearance on David Letterman's "Late Show" in February was a public relations nightmare.
There to promote "Two Lovers," possibly his last film as an actor, Phoenix was either unsmiling, unresponsive or monosyllabic for most of the interview. At one point, he insulted the audience members, who couldn't help but laugh at him. Then he nearly got into a tiff with Paul Schaffer when Schaffer laughed at him. After that, he took the gum out of his mouth and stuck it on Letterman's desk.
When Letterman ended the interview with, "Joaquin, I'm sorry you couldn't be here tonight," Phoenix cracked his first real smile of the night and the audience was left wondering if Phoenix's whole appearance makeover and career switchover, from acting to hip hop, was for real or really great performance art.
Eddie Cibrian and LeAnn Rimes
At first they both denied it, but the proof was on tape.
In March, Us Weekly obtained security camera images of country singer LeAnn Rimes and actor Eddie Cibrian, both married to other people, making out during an intimate dinner at a Los Angeles restaurant.
"She is having an affair," senior editor Ian Drew told ABCNews.com at the time. "It's not even a joke or speculation or from a shady source.
"Even if she did deny it, she would look like a liar," Drew added. "She's on video making out with him. She can't deny it. It happened. There are no ifs."
Cibrian and Rimes, who met on the set of the steamy Lifetime movie "Northern Lights," never 'fessed up to an affair, but both their marriages ended shortly after the Us Weekly cover story. Cibrian's wife, model Brandi Glanville told the magazine in July that she was leaving him because of the reported affair. "Eddie and LeAnn deserve each other," she said.
She was the unlikely singing sensation who shut up notorious critic Simon Cowell.
When Susan Boyle made her first appearance in April on the U.K. talent competition show "Britain's Got Talent," Cowell took one look at the frumpy middle-age Scotswoman with frizzy brown hair and bushy eyebrows and smirked.
Then Boyle brought audience members to their feet with her rendition of "I Dreamed a Dream" from the Broadway hit "Les Miserable," forcing Cowell to admit that he had misjudged her.
The video of Boyle's first performance went viral on YouTube, racking up hundreds of millions of hits, before her erratic behavior became known. But Boyle's performance became a triumph for middle-age women in a culture obsessed with youth and physical beauty.
Boyle would ultimately come in second on the show. But it doesn't matter because her album has already sold millions and she draws crowds with every appearance.
There's nothing new about the Lohan family playing out their spats in public.
But patriarch Michael Lohan upped the ante in November when he released an audio recording of daughter Lindsay Lohan making a desperate plea for help in an August phone call to him.
In between sobs, Lindsay could be heard complaining about her family and ex-girlfriend Samantha Ronson.
"Mommy says that I'm worse than you were," Lindsay could be heard crying to her dad. "She doesn't back me. She doesn't stand by me."
"No one cares about me," Lindsay continued. "They don't, by the way. It's about how they feel, not how I feel. It's not about me. It's never been about me, unless I fight for it."
After Michael Lohan released the recording to Radar.com, his daughter shot back via her Twitter feed.
"Its so sad that I even have to share this w/everyone, but I haven't had a real relationship w/Michael Sr. In years. That is the truth. Xox," she tweeted.
Her father told ABCNews.com that he released the tape to prove his credibility to his daughter, ex-wife and the world at large. He called her declaration that they "haven't had a real relationship" in years, "a total lie. Every time she has a problem she calls me and I come out here."
Jon and Kate Gosselin
When Jon and Kate Gosselin announced they were separating in June on their popular reality show, "Jon & Kate Plus 8," 10.6 million viewers tuned in; the most ever in the show's history.
It seemed only fitting that the family that came to fame by allowing TLC cameras to document the raising of their eight children, a set of twins and sextuplets, would announce the end of their marriage on television.
The announcement came after rampant tabloid rumors of infidelity and speculation about the breakup of their marriage. In some ways, though, it marked the beginning of a he-said-she-said tug of war that dominated headlines for the rest of the summer and well into the fall.
In the end, the publicity turned viewers off and after TLC fired Jon and announced a new show with just Kate and the kids, he refused to give his permission to let the kids be filmed. That spelled the final ending of the show.
Ironically, the kids seemed more distraught over losing the show than their parents' impending divorce.
"They cried in the van on the way home from school the other day. I finally admitted to them, they kept asking, 'Where's the camera crew? Where's the camera crew? We miss them.' And I said, 'Our show is over.' ...Eight sobbing kids driving home from school," Kate Gosselin told ABC News' Barbara Walters.
The most touching moment of Michael Jackson's lavish star-studded memorial service came at the end. Jackson's 11-year-old daughter, Paris, took the microphone in an emotionally charged moment that was captured live during the July memorial and beamed around the world.
"I just wanted to say, ever since I was born, Daddy has been the best father you could ever imagine," said Paris, flanked by her aunts Janet and LaToya and uncles Jermaine and Randy and grandmother Katherine.
"And I just wanted to say I love him so much," Paris said before she clenched her eyes tightly shut, burst into tears and threw herself into Aunt Janet's arms.
What made Paris' remarks even more memorable was that she had never before spoken in public and had rarely been seen without her face covered. With her simple words, Paris conveyed that Jackson, even with a stellar career marred by scandal and charges of child abuse, was simply "Daddy" to her.
Adam Lambert's live provocative performance at the "American Music Awards" touched off a firestorm in November.
Promising before the show to break new ground, the openly gay rocker rode on the backs of his leashed male dancers, brought another male dancer's face to his crotch and made out with his apparently straight male keyboardist Tommy Joe Ratliff.
ABC, which aired the AMAs, said it received 1,500 complaints, most of which the network termed "moderate," but enough that producers decided to edit out the crotch shot when the show re-aired on the West Coast.
Two days after the show aired, "Good Morning America" cancelled Lambert's scheduled appearance. "Given his controversial live performance on the AMAs, we were concerned about airing a similar concert so early in the morning," according to a statement from ABC.
The "American Idol" runner-up refused to apologize for his performance.
"I don't feel I owe anyone an apology for anything," he told Ryan Seacrest on his radio show. "I performed, it was late night TV, I did something that female performers have been doing for years, no different. It's just the fact that I'm me and it's a little different for people. It's really not that big of a deal."
Tiger Woods learned the hard way: be careful what you leave on voice mail.
His voice mail to cocktail waitress Jaimee Grubbs broke open one of the biggest celebrity sex scandals and could cost the golfer his multimillion-dollar endorsement deals and his marriage to wife Elin Nordegren.
Earlier this month, Us Weekly released a voice mail recording provided by Grubbs that she said Woods left on her phone three days before he mysteriously crashed his SUV outside his Florida home. On the recording, a man Grubbs said was Woods asked her to remove her name from her outgoing voice mail message because his wife found his phone and might try to contact her.
"Hey, it's Tiger. I need you to do me a huge favor," Woods said in the message. "Can you please, uh, take your name off your phone? My wife went through my phone and may be calling you. If you can, please take your name off that and, um, what do you call it, just have it as a number on the voice mail. Just have it as your telephone number. You have to do this for me. Huge. Quickly. Bye."