Mark Pilgrim got a going over from Hixie which he then implemented, however he now claims to be accessible to WAI AAA, seen as his site isn’t even readable by me, I don’t think it’s really true. Unfortunately he’s using Bobby as the arbiter of accessible, even with its recent improvements, it’s still a tool, and cannot decide if something is accessible. Mark even claims the accessibility problem is something to improve accessibility! If you specify a background colour, you must specify a colour for the foreground - including links - aswell, Mark sets the background colour white, but doesn’t bother setting the link colour. Fine if your default link colour is blue, completely useless if your default link colour is white.
The same problem was picked up Hixie, in his report on AaronSw’s weblog so no-one should have any excuse.