Scots Guardsman Cameron Reilly, 18, who usually stands guard outside the royal palace, called Prince William's bride-to-be a "posh b****" and other nasty names on the social networking site, the U.K.'s Press Association reported.
Watch a special "20/20" Thursday at 8 p.m. ET for a behind-the-scenes look at the life that awaits Kate Middleton and join us again at 4 a.m. Friday morning for ABC News' live coverage of the Royal Wedding with Diane Sawyer and Barbara Walters.
Reilly reportedly wrote, "hur and william drove past me on friday n all a got was a sh*tty wave while she looked the opposite way from me, stupid stuck up cow am a not good enough for them! posh b**** am totally with u on this 1 who reely gives a f*** about hur".
Reilly also posted anti-Semitic and racist comments on his Facebook page, the Press Association reported. The Ministry of Defense is reportedly investigating the claims and has removed Reilly from his wedding day duties.
The embattled guard is not the first to bear the scars of misusing social media. Below are seven other people who tweeted or Facebooked their way into trouble.
NYC Aide's Facebook Post About Obama Leads to Resignation
You may think your Facebook page is personal, but depending on what you share, your posts could lead to professional consequences.
An aide for a New York official resigned in July 2009 over comments posted to Facebook about the controversial arrest of Harvard professor Henry Louis Gates Jr.
At the time, City Hall News reported that Lee Landor, deputy press secretary for Manhattan Borough President Scott M. Stringer, referred to President Barack Obama as "O-dumb-a" on her Facebook page.
According to screen grabs of the Facebook posts on City Hall News' Web site, Landor wrote in one post, "O-dumb-a, the situation got "out of hand" because Gates is racist not because the officer was DOING HIS JOB!"
The screen grabs also indicate that, during workday hours, Landor had an ongoing debate with several other Facebook members about the Gates incident.
In another post, Landor wrote, "And racial profiling does exist, but for good reason. Take a look at this country's jails: who makes up the majority of inmates? Exactly."
ABCNews.com could not immediately reach Landor for comment.
But Dick Riley, communications director for Stringer told ABCNews.com, that the office learned of the posts from the City Hall News story and issued a statement Monday evening about Landor's resignation.
"Ms. Landor's comments were totally inappropriate and in direct contradiction to the views of the Borough President and his office. The Borough President has accepted Ms. Landor's resignation, effective immediately," Riley said in the statement.
Schwarzenegger Wields 2-Foot-Long Knife on Twitter
In a 27-second clip posted Tuesday, the husky governor addresses the Twittersphere while holding a 2-foot-long knife.
As the state wrestled with a $26 billion deficit, the celebrity turned Republican governor posted the video as a thank you to constituents for their ideas on how to pay down the massive deficit, particularly one suggestion to autograph and then auction off state-owned cars.
"Hey guys, I just want to say thanks very much for all the great ideas you're giving me," he said. "You come up with great ideas. Why not just sign the cars since you're a celebrity governor? Sign the cars and sell it for more money. … That's exactly what we're going to do."
According to The Associated Press, Schwarzenegger's spokesman Aaron McLear said the knife was a gift from a friend and arrived Tuesday. He also said the governor actually does intend to sign state vehicles before they're auctioned off in late August. Officials estimate that selling 15 percent of the state's 40,000 government-owned cars could raise about $24 million.
When a reporter asked Schwarzenegger Wednesday whether the video was appropriate, given how seriously the budget cuts are affecting the lives of some Californians, the governor went on the defense.
"Not that I have fun with making the cuts -- they sadden me -- but ... that doesn't mean that you cannot wave a knife around, or to wave your sword around, to get the message across that certain cuts have to be made because it's budget time," Schwarzenegger said during a news conference.
Arizona Man Says Tweeting About Vacation Led to Robbery
If you're heading out of town, should you think twice before tweeting it out to your followers?
One Arizona man thinks so.
Before leaving with his wife for a summer vacation in 2009, Israel Hyman told his approximately 2,000 Twitter followers that they were "preparing to head out of town," that they had "another 10 hours of driving ahead" and later, that they "made it to Kansas City," CNET reported at the time.
But when they returned home, they found that someone had broken into their home and stolen video equipment he used for his video business -- to the tune of a few thousand dollars.
"My wife thinks it could be a random thing, but I just have my suspicions," he told The Associated Press. "They didn't take any of our normal consumer electronics.
"The customers have never met me in person," Hyman said. "Twitter is a way for them to get to know me. I forgot that there's an inherent danger in putting yourself out there."
Det. Steven Berry of the Mesa Police Department, which is investigating the burglary, said, "You've got to be careful about what you put out there. You never know who's reading it."
Al Roker Tweets From Jury Duty
In May 2009, "Today" show weatherman Al Roker found himself in a blizzard of headlines when he snapped photos of potential jurors on his iPhone and -- in violation of court rules -- posted them to his Twitter page.
Newspapers had a ball, with the New York Post headlining a story with, "Oh, What a Twit!" But Roker promptly apologized to officials at Manhattan's Criminal Court. He called the mistake "inadvertent," but defended himself.
"Folks need to lighten up," he said in a later Twitter posting. "I'm not breaking laws ... just trying to share the experience of jury duty. One that I think is important and everyone should take part in."
David Bookstaver, a spokesman for the state Office of Court Administration, echoed Roker's sentiment, while saying the picture taking was "ill advised."
"No harm was done," Bookstaver said, adding, "What's more important is this shows Al came to do his civic duty, and we're happy about that. It's a good example that nobody's exempt."
Mavericks Owner Slapped With $25k Fine for Tweeting
In March 2009, the NBA came down hard on Mavericks Owner Mark Cuban for tweeting grievances against referees. The NBA hit him with a $25,000 find for publicly criticizing officials after the Denver Nuggets beat his team, the Dallas Mavericks.
Using Twitter, he complained that Denver's J.R. Smith was not called for taunting Antoine Wright after he missed a shot.
After he heard about the fine, he wrote, "can't say no one makes money from twitter now. the nba does."
Top House Republican Tweets From the Green Zone
We all want our elected officials to be transparent in their motivations. But maybe there's such a thing as too much transparency when Twitter is involved.
In February 2009, Rep. Pete Hoekstra, R-Mich., found himself in a bit of hot water when he updated the public on his travels through Iraq and Afghanistan.
"Just landed in Baghdad," the congressman declared on Feb. 5 at 9:41 p.m., The Associated Press reported at the time.
Later that evening, he disclosed more details: "Moved into green zone by helicopter, Iraqi flag now over palace. Headed to new U.S. embassy. Appears calmer, less chaotic than previous here."
Hoekstra said he wasn't in the wrong, pointing out that other high-level officials also tweet their travels.
But the episode led the Pentagon to review its policy, as it views such information as sensitive, The Associated Press reported.
Tech Expert Asks for 'Do-Over' on Twitter
Sometimes, even the most tech-savvy of the technorati run into trouble online.
In March 2009, New York Times consumer tech columnist David Pogue shared his personal phone number with a few too many people when he first started getting used to Twitter.
Thinking he was sending private notes to just a few Twitter friends, he let loose a message with his phone number included.
Imagine his surprise when he realized that he had sent the number to 21,000 Twitter followers instead.
Within seconds, he wrote in a column, he realized his mistake and followed up as fast as he could: "YIKES! I'm so sorry, that was meant to be a direct message. Have mercy ... Please disregard my phone number!"
A follower recommended that he delete the post, which Pogue didn't even know he could do.
But he said that the crowd was sympathetic. Not a tweeter called his number and one wrote, "You'll be ok. Folks are respectful when it really counts."