Who Could Replace U2 at Glastonbury?

According to official sources, Bono just had emergency back surgery, putting the upcoming U2 tour in jeopardy, most notably their headlining performance at the Glastonbury Festival of Contemporary Performing Arts. While rescheduling other tour dates is sure to be a logistical nightmare with baseball and football in the equation, Glastonbury only happens one weekend a year, with a fallow year every five years or so, so it doesn't have that luxury. Back surgery is a serious procedure, and with the performance less than five weeks away, will there be enough time to make a full recovery? Playing Glastonbury is important to the band and Bono will want to give it his best, so if there's a significant chance he won't have fully recovered and rehabilitated by then, cancellation seems likely. Official word either way is expected next week.

If U2 does have to cancel, what act would fill in for them? Specifically, what artist is both able and willing?

Pulp
Why? Would be the best thing to ever happen.
Why not? Still not reunited.

The Libertines
Why? Pete Doherty is a Glasto favourite.
Why not? Exclusive to Reading/Leeds.

David Bowie
Why? Previously rumored, everybody wants to see Bowie.
Why not? Hasn't played live in over five years, isn't going to start now.

Rolling Stones
Why? Previously rumored, have never played, superstars.
Why not? Still not on tour.

Paul McCartney
Why? No gig scheduled that day.
Why not? A performance at Millennium Stadium on Saturday and Hard Rock Calling on Sunday would mean three shows in three days, something acts of that caliber don't do.

Pearl Jam
Why? Popular, never played.
Why not? Playing Hard Rock Calling that night.

Jay-Z
Why? Silenced naysayers when he headlined in 2008.
Why not? Too soon for a return.

The Prodigy
Why? Touring but currently no gig on that day.
Why not? Played last year.

Arcade Fire
Why? Popularity went through the roof thanks to phenomenal live shows, just like U2 in the 80's.
Why not? Glasto would be their first live show in ages, plus they already sold out to Reading/Leeds exclusivity.

Prince
Why? Headlining Roskilde the following weekend, legend, has never played Glastonbury, would be as impressive of a booking as U2.
Why not? Famously difficult to book, and would he agree to being broadcast on the BBC?

Lady Gaga
Why? No performances scheduled that weekend, no issues with exclusivity at any competing festivals.
Why not? Performed in 2009 and already received an incomprehensible amount of media attention over it.

Beyonce
Why? Was rumored late last year, beloved pop star, husband famously headlined in 2008.
Why not? Would be a controversial choice even under normal circumstances.

Gorillaz
Why? No gigs scheduled that weekend, Mos Def and Snoop Dogg will already be playing.
Why not? Damon Albarn headlining two years in a row?

Radiohead
Why? The other major contender for best live act in the world. Their previous headlining sets were pure magic.
Why not? Recording next album.

Atoms for Peace
Why? Atoms for Peace have yet to appear in Europe.
Why not? Despite their popularity, they aren't billed as a headliner at other fests. Thom might be too busy recording at the time.

The Chemical Brothers
Why? Strongly rumored for months, still rumored despite a debunk from Emily Eavis, still tweeting about being at Glastonbury, only to delete them. A live show with a full production on the Pyramid is a proven crowd-pleaser.
Why not? Already an excess of big electronic acts closing out their respective stages on Friday night.

Coldplay
Why? Were rumored for a secret set in 2009, then were rumored to open the fest in 2010. While neither of these rumors panned out, maybe there was something to them. Michael Eavis recently said they might play next year. Chris Martin is a noted U2 fan.
Why not? Not currently touring, although it wouldn't take long for them to get ready for another show.

Kings of Leon
Why? Playing Hyde Park the following week, no gigs scheduled during Glasto.
Why not? Too soon, V Festival two months later may or may not be a factor.

Rolf Harris
Why? Hugely popular among Glastonbury punters, so much that police had to block off the dangerously overcrowded Jazzworld area during his set last year.
Why not? Will an early-in-the-day nostalgic novelty work as well at the end of the night?

Dizzee Rascal
Why? Even more popular than when he performed last year, and it would not be the first time a pre-headling act on the rise gets promoted to headliner (Pulp filling in for Stone Roses in 1995).
Why not? Major difference in popularity between Dizzee Rascal and U2.

The Flaming Lips
Why? The Flaming Lips live show is made for festivals, and the Other Stage headliner (Basement Jaxx) filled in when Kylie Minogue had to cancel in 2005.
Why not? Also a significant difference in popularity between them and U2.