i agree that there's no way that much damage would be done from tapping the wheel... i've seen people come a lot closer to injury, or actually get hit, on a critical mass ride and there isn't even any damage done. but then again, i've never been on a san fran critical mass.
a critical mass ride of 3000, if that first report is true, seems huge to me. even the biggest ones i've been on in philly haven't even come close to that. i can see how in a crowd of 3000 a few kids with itchy u-lock arms could turn a situation bad and the level heads might not be able to do anything about it.