I feel MeFi is a bit allergic to the politics of HN. For example, the recent Google discussion would have gone over very differently there. (I say this without passing judgement, since I tend to ping-pong back and forth between both sites.)
I do in fact love those kinds of MeFi threads, and I credit them with broadening my understanding of the world and helping me become a better feminist. I think many HN users wouldn't feel comfortable in that sort of discussion, however.
HN always felt like a bit of the agora, with the occasional thunderbolt from dang to shut down flagrant shitposting; MeFi seems more civil. People seem more caring there.
There is, right now, a fairy large (for MeFi - something like 1000+ comments at this point IIRC) discussion on that topic on MeFi. I think the moderators have been hard at it given the contentious nature of the topic.
My suspicion? A lot, and most of it from the older Metafilter users who, like me, miss the heyday of the link blog. That's basically what I use HN for.
