some of the same crowds from protests/may day are at CM, for sure - but you'll also see lycra-clad, reflective types too. i've even seen recumbents there.

did you know? the first known CM (well, it was a bike protest anyway) was in SF back in the early 1900's - i need to dig out my CM book to get details on that.

i think CM started as a ride-protest (for me), but now when i go i'm just out to have fun. many drink before/during/after (i don't). so it's more of a celebration of bikes than anything else.

one thing i will say is that the people there have bikes as a major part of their life - as opposed to a hobby that you just do on the weekends.

the other thing is that no two CMs will be alike - every city is different, for instance in Paris they do it on Saturday morning I'm pretty sure, instead of the last friday of the month at rush hour.