I can't say anything about CM events elsewhere, but the recent one here in Seattle, during which "corking" was applied and a couple of cyclists arrested, was appallingly counter-productive. Irritating a lot of people who are trying to make a living just makes all cyclists, whether they took part in the event or not, look like a bunch of immature losers who don't have anything better to do than to mess up traffic, and makes it less likely that the people (e.g., city government) who are in a position to promote bicycle use will be inclined to do so. The net effect is to make the environment MORE hostile to bikes. The people who organize such events should be severely beaten with U-locks, and forced to move to Houston. (My apologies to those of you who live in Houston.)