Rumors of mimed and lip-synced performances have followed Eminem for years, but they are definitely resurfacing in a big way after his performance this past weekend at the T in the Park Festival in Scotland. The show was Em's first U.K. performance in five years and he chose to highlight some of the stadium-ready tracks from his recent 'Recovery' album. Nonetheless, fans were skeptical and claimed that much of the performance was fake.

"His miming was awful," said one attendee. "At one point, he tried to say something and his mic was off."

Another claimed Em didn't even know what city he was in -- an insult to the Scottish people. "He mimed at a supposed live festival and didn't even know he was in Balado. He seemed to think he was in Edinburgh."

It's worth pointing out that there's a big difference between outright miming a performance (think Ashlee Simpson on 'Saturday Night Live' a few years back) and using a pre-recorded vocal track to boost a performer's voice for a large performance. Nearly every rapper that hits the stage at a festival, major arena or large club performs over some preset backing vocals. Check out this video and judge for yourself.