they are the first (night) headliner. the hypothetical i said earlier applies to any headliner, there should be name and music recognition. muse have a string of mainstream hits from the last decade that is probably going to continue for years to come, and arcade fire have been steadily bubbling the last few years to the point where they can be a coachella headliner. what they lack in truly crossover hits they make up for in album of the year grammys (more recent than outkast's), #1 billboard debuts, sold out concerts at madison square garden, and high-profile collaborations and appearances on shows like SNL. as crazy as it may seem to some of us, outkast doesn't have or at least no longer has these things.