NIN and RATM headlined in 08 too. Cypress Hill is there this year, but not a headliner.
Seems like the bigger artists are starting to join in. Definitely the indie crowd is getting in to it. Still not seeing Lady Gaga or the other big summer arena shows get in on it. I imagine Tom Petty will still show.
Tom Petty was the voice of Lucky on King of the Hill, one of my favorite conservative-minded-shows (not sure if it was, but it seemed that way), maybe he's not a liberal dimwit.