I talk to a lot of people, including some who post fairly regularly, who are deeply affected by conversation on the boards. I think that some people just can't handle being attacked or challenged and such and so they are reluctant to post because, even in cyberspace, it feels to them like they're being "beaten up" if someone challenges them.

I think that's a big part of the reason for lurking.

And, like Michael said, sometimes you want to lurk and read and learn and not post for fear of creating a flame war or otherwise not being appreciated.

When I post at a place like GFY where I *know* people are just rude, I just pretty much assume I'm going to get flamed, but I think some people just don't have the stomach for that.