I've been a part of a few of those critical mass protests, at first glance it appears like a good thing to participate in - increasing awareness of cycling as an option to people that might not be familiar with it.

But the combative mindset that seems to be a core part of the tradition only seemed to polarize people and actually put us further back from our (supposed) goal of increasing accessible cycling infrastructure. At the last one I was almost embarrassed to be there. And some people do legitimately need to get somewhere on time, to take liberties with that is unnecessarily off-putting.

I now think it's much more about feeling like you're part of an in-group, a persecuted and rebellious one at that. I'm now much more a fan of the (boring?) folks calmly working for greater cycling access, and having much more success at it.