....or my sense of humour, either!
Here in the US, critical mass demonstrations usually attract the same crowd of anarchists and rabble seen in recent years trashing Seattle's downtown or Quebec City's downtown during the "G8" world meetings. On their best days, the reason for the rides is merely to tie up as much traffic as they possible(especially the group in San Francisco) on friday afternoons. Once, they ran handlebar-to-handlebar across the golden gate bridge at 5 mph, then back again!
These people are not trying to further the use of bicyles, but rather are using the bicycle as a method of public irritation. I've read stories recently of increased motorist hostility towards cyclists in and around the bay area, and I would bet that critical mass is the reason why this is happening.
Don't let these clueless radicals hijack our favourite pastime!