It was about time for another Brit-Brit scandal.
The on-the-rebound pop princess is causing controversy again, accused of lip syncing on stage during the Australia leg of her "Circus" tour.
According to People magazine, about 100 infuriated fans ditched Spears' Perth show Friday, blaming her subpar performance and lack of real singing. The following day, singer/songwriter John Mayer, who's also in the Outback, posted the following update to his Twitter account:
"If you're shocked that Britney was lip-syncing at her concert and want your money back, life may continue to be hard for you."
Ouch. ABCNews.com's calls and e-mails to Spears' publicist for comment were not immediately returned.
It's not the first time Spears has been accused of lip syncing, and she's certainly not the only star to come under fire for it. Below, check out a run down of five uber controversial alleged lip-syncs, and the verdict on whether or not each artist committed what many fans regard as the greatest on-stage sin of all.
No one ever said it would be easy, Yeezy.
Kanye West added himself to the roster of music's most infamous on-stage mishaps in December 2008 when he failed to nail his performance of "Love Lockdown" on "Saturday Night Live."
To be fair, West's greatest strengths lie in rapping and producing.
"Love Lockdown" and the album from which it hails, "808's and Heartbreak," are West's first foray into singing. But whether by his own fault or because of his audio equipment, his attempt to serenade "SNL's" audience came off as feeble at best, fueling rumors that he requires a little help in the vocals department.
From the moment West got on the mic, it was clear something wasn't right. Rob Levine, executive editor of Billboard magazine, speculated West's weak voice had to do with a glitch in the autotune feature many artists use to stay on pitch while recording in the studio and rocking out live.
"Autotune allows you to hit every note perfectly. You're not going to be sharp or flat," Levine said. "I think the effect wasn't fully realized, [the autotune] might have been set up wrong. But it's foolish to suggest he was lip-syncing. If he were lip-syncing, it would've sounded exactly the way he wanted it to."
Even if West didn't lip-sync, Tyler Gray, Blender magazine's senior editor, didn't let him off the hook.
"He was cheating. At the end of the day, did he make up for that lackluster element of his performance with something that balanced it out? I don't really think so. It was neat visuals, but the music wasn't quite up to par," said Gray.
"In the beginning, he got an A for effort because he was trying to break the mold," Gray said, referring to West's branching out from typical hip-hop techniques. "But the effort grade only goes so far. Now he actually has to sound good. And he didn't. He sounded like a bad talent show."
With pop stars like Spears, it's all but expected that lip-syncing will go hand-in-hand with a live performance. Levine called it an open secret in the music industry, the product of audiences expecting artists to sound the same on albums and on stage.
Do Fans Come to Hear Britney or See Britney?
"Traditionally, jazz and opera had singers who were technically great singers, whereas in rock you had singers. But if they were a little sharp or a little flat, but no one really cared because they weren't expected to be perfect," he said. "As pop music becomes more artificially perfect, kids who grew up on that aesthetic want that perfection. When you're used to everything being on pitch, you don't want to hear anything else."
As a result, stars like Spears often perform with backup tracks to ensure they sound as perky and on pitch on stage as they do on their albums, after producers spend hours fine-tuning their voices.
Spears' November 2008 performance of "Womanizer" on the U.K. TV show "The X Factor" was panned by critics because she reportedly lip-synced although "X Factor" judge Simon Cowell didn't seem to mind. The "American Idol" mainstay gave the rebounding pop icon a standing ovation after her gig.
Levine thinks fans should stop expecting everything from Spears and her ilk.
"No one is going to go see Britney because she's a great musician," he said. "She's a good singer, but she's a personality. She's a phenomenon. She's not an artist, she's a pop star.".
But Tyler argued that Spears could up the ante, saying her "dancing is pretty physical but it's not so grueling that she shouldn't be able to sing as well."
Unlike Spears, Madonna's routine on her Sticky & Sweet world jaunt and on tours past is more suited to marathon runners than musicians.
The 50-year-old queen of pop performs high kicks and running jumps as she bounds across stage, yet never seems to struggle for breath. It's a tell-tale sign she's probably performing with a backup voice track.
"If you look at the way pop stars perform, the way they're twirling, running, being carried, dancing on the stripper pole upside down -- they can't possibly be singing every word of every verse," said Levine. "A lot of times it's blended, they might be singing with a safety net. Any pop singer putting on a full dancing show is not singing every word in those songs. The fact that they're not breathing hard should be enough to clue you in."
At London's annual Q Awards show in 2004, Elton John bashed the pop star for not performing up to par on her Re-Invention tour, saying "Madonna, best f-- live act? F-- off. Since when has lip-syncing been live? Anyone who lip-syncs in public on stage when you pay [about $169 per ticket] to see them should be shot."
Madonna Denies Lip-Syncing
Liz Rosenberg, the Material Girl's publicist, shot back, "Madonna does not lip-sync, nor does she spend her time trashing other artists. She sang every note of her Re-Invention tour live and is not ashamed that she was paid well for her hard work."
The debate didn't stop there. In an attempt to help out his pop star friend, actor Rupert Everett added fuel to the fire, telling the British press, "Madonna sings everything she can sing. ... But, if she goes into a dance routine, she's got to dance. You can't breathe and dance and sing at the same time."
Some stars couldn't cry libel or count on their celeb friends for defense when it comes to lip-syncing accusations.
Ashlee Simpson, the pop-punk younger sister of Jessica Simpson, learned that after her headline-making October 2004 blunder on "Saturday Night Live."
Attempting to perform "Autobiography," her second song of the night, Simpson found herself singing along to the music and lead vocals of her first song "Pieces of Me."
She held the microphone at her side as her canned voice boomed across the studio, danced an awkward jig and then ran off the stage as the vocal recording was shut off and NBC cut away to a commercial.
At the end of the show, "SNL" host of the night Jude Law quipped, "What can I say? Live TV." Simpson, standing next to him, blamed the mishap on her musicians. "My band started playing the wrong song," she said. "I didn't know what to do so I thought I'd do a hoedown."
A statement issued by Geffen Records, Simpson's label, claimed there was "a computer glitch," while a representative for the show said that the song that came up was a backing track.
The following Monday, Simpson called into MTV's "Total Request Live" and explained that because of complications arising from "severe" acid reflux she had lost her voice and that her doctor had advised her not to sing.
But the incident tarnished Simpson's rep for months. In January 2005, Simpson performed "La La" during the halftime show for the Orange Bowl in Miami and got boos from the crowd of more than 70,000 spectators.
Simpson attempted to build credibility in '05 with a U.S.-Canada tour that she described to reporters as "stripped down," without effects like pyrotechnics, just "me and my band getting out there and having fun."
Then there are the lip-sync scandals that taint an act for life. In 1989, the dreadlocked duo from Deutschland were performing their hit "Girl You Know It's True" during an MTV-recorded show in Bristol, Conn., when their vocal track began to skip. While fans at the concert didn't seem to care, critics took note and began questioning the merits of Milli Vanilli members Rob Pilatus and Fab Morvan.
Lip-Syncing No Longer Shocking
A year later, in November 1990, press scrutiny led the group's manager to reveal that Milli Vanilli didn't actually sing on their Grammy and American Music Award-winning records.
Four days later, the band's 1990 best new artist Grammy was withdrawn. Arista Records dropped the duo from its roster and deleted their album from their catalog, taking "Girl You Know It's True" out of print.
Despite subsequent albums and attempts at a comeback, Milli Vanilli never shed their status as one of pop music's most legendary cautionary tales, an example never to be repeated by reputable artists. Though, Levine emphasizes, nearly two decades after the Milli Vanilli debacle, lip-syncing is still going strong.
"Years ago, when it was revealed that Milli Vanilli was lip-syncing, it was practically a scandal. People were honest to God shocked," he said. "These days, anyone who's the least bit surprised by this is really naive."