I've just been looking at ticket sites for this, and all of them still have seats available, some even on the not completely sucky lower tier, fairly close to the stage (highlighted).
The Wembley show last year must have satisfied demand, and the raft of filler support bands have no draw. Knowing the Cure are only playing a 90m set can't help either. That said, the NME should have had the power to sell this event out by now. Could this be a result of the Credit Crunch? "I saw the Cure last year, sod dropping £30 plus booking again"
On a Cure related tip, Geffen have just released news about 'fake Robert Smiths' prowling the net here. Made me chuckle, anyway.