Beyonce might be the person who's taking the most heat for lip-synching at this precise moment in time, but she's far from the first performer who has relied on a backing track of some sort. While she stands a good chance at recovering from her national anthem trickery, some earlier musical offenders weren't so lucky.

Milli Vanilli was famously stripped of the best new artist Grammy in 1990 after it was discovered that they -- Robert Pilatus and Fabrice Morvan -- didn't actually provide the vocals used on their "Girl You Know It's True" album. Below is one of their hit songs from the album, "Girl I'm Gonna Miss You," which hit the top of the charts when it was released in 1989.

There's the behind-the-scenes lip-synch, and then there's the live, right-before-your eyes reveal. Despite the fact that the original clip has pretty much been scrubbed from the Internet, Ashlee Simpson will long be remembered for her "Pieces of Me" fail on "Saturday Night Live" in 2004. The music started, but her mouth didn't really move, and Simpson did a little jig to deflect the awfulness of the situation. (Catch some of it around the 3:50 mark of this video.)

In October 2012, Justin Bieber made headlines for throwing up on stage -- hey, stars get the flu, too! -- but the other takeaway was that while the singer was losing his lunch, he managed to keep on "singing."

Pop stars aren't the only ones guilty of relying on pre-recorded vocals. Is rapper Eminem's mouth keeping up with the vocal track here?

At the 2007 BET awards, 50 Cent skipped the entire first verse for "Amusement Park" and wandered the audience until catching up with the song. Did he forget the words? Later he said, "I just wasn't concentrating."

These examples just scratch the surface; where proof exists of one artist lip-synching, there are scores of allegations that others are doing it, too. Mariah Carey, Britney Spears, Madonna, the list goes on.

Are you bothered by lip-synching or is it enough to see a performer live on stage, whether he or she is actually singing or not? Weigh in on Facebook.

Related content:

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Curtis "50 Cent" Jackson

Judging by his recent comments on Twitter, rapper 50 Cent is not feeling optimistic. "I don't think I'm gonna live much longer," he wrote during a series of tweets that began on Monday. Earlier Tuesday, he clarified the remark: "To be conscious that life is short is not suicidal," he wrote. "I'm good if I die tonight."

The rapper also claimed that he has "lost all the faith in the team I'm on. I have nothing left to say. I will not be promoting my music." The comment comes after months of discord between the artist and Interscope Records, who are expecting the delivery of his next album. Last month, 50 Cent released the self-produced mixtape "The Big 10," marking the 10-year anniversary of "50 Cent Is the Future."

If he's disillusioned with the music industry, he has plenty to keep himself busy. Most recently, 50 has been concentrating on promoting Street King, his new energy drink, proceeds of which are earmarked to fight world hunger. At an event last month for the launch of his new line of headphones, 50 Cent talked to Rolling Stone about signing "Jersey Shore's" Pauly D to G-Note Records.

What do you think of the rapper's comments? You can discuss them on Facebook.

Related content from Rolling Stone.com:

• 50 Cent Says Pauly D Is a Mix of DJ Drama, DJ Khaled and David Guetta
• 50 Cent: 'I'm Not Releasing an Album'
• Van Halen to perform at tiny New York club