The Vancouver Critical Mass goes against the original intent IMO. I'm all for improving the city cycling experience but pissing off motorists is counterproductive.
From the Critical Mass site:
CM is intended to be a celebration, not an opportunity to cause trouble. Those who want to try to tie up traffic as much as possible and be confrontational with motorists are missing the point. We can assert our right to the road without being rude about it. Focus on the ride, not on the cars that also happen to be on the road.