As soon as Bain denied MJ was performing, the WMAs press guy came out with a statement that MJ was doing something special for his fans. Accepting an award doesn't fulfill that criteria. And we know that the choir was hired a week in advance and told they'd be singing with MJ.
There was some insider info posted on one of the fansites at the time - that there had been loads of cock-ups that night. MJ's award was apparently supposed to be preceeded by a video montage, but that didn't happen. His award was apparently supposed to be presented centre stage rather than on the balcony.
I heard he actually rehearsed a couple of songs but never ended up singing them for some reason. MJ claimed on the red carpet that it wasn't a performance, but if that's the case, why was the choir hired a week previously and told they'd be singing with Michael Jackson?
I think it emerged that MJ was paid as a live performer for the night, too.
What happened with the fan party?