Lollapalooza Playing Games, Too?

I don't know what's going on, but Music Festivals are loving to play games with the fans, these days. This might even be worse than the Bonnaroo Lineup Announcement, that took like 16 hours, on Twitter, and MySpace.

Lollapalooza's Lineup is out on April 6th, and, they have put out a poster, with boxes, and the only letter is O. Want to guess?