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."