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.