Anyone heard of Critical Mass?

Apparently it's a regular protest held by cyclist's in cities all over the world against car culture, pollution, and bicycle-unfriendly city streets.  But it has no leadership or structure and thus no clear goals.  On the last friday of every month hundreds of cyclists meet in a designated spot and roam around the city disrupting traffic.  Their slogan is "we aren't blocking traffic, we ARE traffic".  The route is never planned, the group just kind of wanders under the direction of whoever happens to be riding at the front.
I stumbled on this movement by accident.  Last friday (the last friday in April) I was riding home when I found the major street near my place in Montreal to be completely blocked off by hundreds of bikers.  I asked one guy what was going on and he said "it's critical mass, we're taking back the streets, come ride with us".  So i rode around with them for a bit to check it out.  The group would ride up the street, often obstructing traffic in both directions, and people would park their bikes across intersections to prevent cars from entering and splitting up the group.  They shouted slogans like "more bikes not  cars".  At one point the group gathered in the middle of a major intersection and everyone raised their bikes over their heads and started screaming (not me, i thought this was particularly retarded), which brought all traffic in that area to a stop.
It should be mentioned though that relatively few people were being majorly beligerent towards the cars.  Overall it had kind of a festival atmosphere with lots of people rocking boomboxes, tricked out rides, unicyclists, etc.  But as far as a protest goes its pretty pointless, and was used by some people as an excuse to cause shit.  I hate gas guzzling SUVs and would love more bike friendly streets and all the rest (got smoked by a taxi last year) but as much as critical mass is a good time its certainly no way to get a point across and gives lots of idiots an opportunity to, uh, be idiots.
Thoughts? For those of you that live in major cities and like to bike you can probably find your local meeting spot on google if u wanna check it out.

(For those of you that live in Montreal, I joined the group at St. Laurent and Sherbrooke, we rode up to Mt. Royal, then across to St. Denis which is where they blocked traffic for awhile.  Then headed down St. Denis and I broke off when they started heading West somewhere near Pins.  Apparently the montreal meeting spot is Philips Square at 5:30, last friday of the month.)