Horace and Dr Crazy have written very smart posts about the blogging panel at MLA, and the experience of meeting up with virtual acquaintances. So far, the main change I've noted is that I "hear" their posts a bit differently than before. Most of the people who I met at MLA were already in my daily core list of blogs, so that hasn't changed. I have spent more time in the last 2 days reading blogs from other people either not previously in my core, or completely unknown to me; some of those might stick in my feedreader, others might not. And, perhaps most significant, the whole little flurry of interest in blogging (at and after MLA) and especially the f2f meetups have revitalized my own interest in blogs. (Plus, of course, my spring semester hasn't started yet. )
Dr Crazy suggests that rather than worry about how or if blogging should count as a form of publication towards tenure, one could better think of it as a form of service. I think this is true of some blogs more than others (her generous discussions of her assignment practices etc are a kind of service to the teaching community, certainly). And personally, I don't see why one would want a blog to "count" towards publication, any more than my department should "count" the articles one of my colleagues writes for his church newsletter. (And yes, sadly, he submits these on his activity report each year.) One of the appealing things about blogging for me is that it is separate from all those dynamics and institutions, and yet related enough that it is academically energizing, soothing, or interesting.
There's another spot on the traditional academic cv that strikes me as equally viable as a comparison for blogging: the section of Professional Organizations (or memberships, or associations, depending on your institution's template). Now, I've always assumed that this is a vestigial remnant left over from Ye Olde Days when membership in one of these Old Boys Clubs actually meant something other than that you paid $45 and receive a newsletter twice a year. Why should any committee care where you spend your hard earned cash? I only belong to those organizations which sponsor the conferences I regularly attend (which usually require membership, a neat tautological circle). Simply belonging to the MLA, for instance, doesn't really say anything about you except that you attend the convention and/or want to receive the journal. Now, if you're an officer, or doing substantial work for an organization, most people would list that under Professional Service on the cv. Membership alone is a much more nebulous thing. It might be significant; it might demonstrate involvement, or activity; but it might not. Having your name in someone's blogroll is sort of similar.
On the other hand, the sense of community I've enjoyed online (and now also in person) is very real, and important. And perhaps comparable to the role that the professional organizations once played in the pre-internet days. Academics need the advice, support, and interest of others in their field -- we need things that our immediate departmental colleagues can't provide (unless perhaps you're in an extraordinarily large and congenial department). Blogging gives me a sense of the larger profession that is different from what I get from attending a major conference -- but both are valuable, and help fill in each other's gaps. Blogging doesn't necessarily replicate the hierarchical structures of academe (which most conferences do) -- some of the most compelling voices I've found have been from persons or positions marginalized within the system.
I'd hate to imagine a future when academics felt "required" to have blogs, or to leave comments on Important People's sites, etc. That's what would ultimately happen if blogging began to "count" within the institutional system. I think it's a much more powerful force for change precisely because it doesn't "count" in the same way as our other activities.