So this guy has been posting in the Mayhem 2012 thread on MetalSetlists about random rumors. I'd say he's talking out of his ass but Wolverine sort of vouches for him. I'm about 50/50 on believing him.
"I have more news about Ozzfest 2012!!
System Of A Down
2nd Stage Headliners:
Lamb Of God
2nd Stage Rotating Order Bands:
All Shall Perish
All these bands are confirmed as of right now!!
There will be 29 dates and all I know is that 3 of them are San Bernadino,CA, Seattle, WA and Bristow, VA!!"
According to him, Lamb of God specifically asked to headline the side stage to help film their new world tour DVD.