James had a few interesting thoughts on the blogging community (and the role he's relegated listservs to).
I have to be honest with you - I'm subscribed to so many lists but I never read any. It usually goes like this: I find a new list that seems interesting. I subscribe. The volume quickly overwhelms me, because of my personal e-mail reading habits, so I switch to digest mode. As soon as I'm digest mode, it's all over. By this time, I've also set up a rule to forward to a particular mail folder in Outlook. At this point, more often than not I find myself marking all as read (if I want to keep the contents for archival purposes) or just deleting them.
Needless to say, I've never found much community in the listservs. I think part of the problem is just that the signal-to-noise ratio is too high, so sometimes it just takes too much effort to get out what you're looking for.
Blogging, on the other hand, seems to suit me well. I was just talking to Scott, and as I mentioned to him, one of the biggest things that has really helped build community here is the dotnetweblogs.com homepage. For one, it's a focused aggregator and it gives you visibility into someone's weblog you might not have found otherwise. I find myself visiting this page repeatedly throughout the day to see what people have written. I don't keep up to date nearly as well on listservs or forums though.
I don't think they can just compete, I think they surpass listservs and the like for community. It's a more scalable model for community building :)
(Also - just wanted to add - I also think weblogs let you get to know someone's personality much better than a simple mailing list)