Conventional academic discourse lies with journals and conferences. For all the advantages of these modes, neither offers an ongoing, dynamic interchange. Listservs offer that, but, in my experience anyway, they don't really create a productive, collaborative space. Sometimes there are debates on listservs; sometimes there is sharing of information (e.g. does anyone know a good article about x"?). But there isn't a sustained building of knowledge there. I suppose there could be, but there isn't, probably b/c we all go off to write our individually authored articles and conference presentations.
In any case, the listserv is too large a community for collaborative work. Yes, tens of thousands contribute to Wikipedia, but they don't all work on the same article, right? So I don't know what the magic number is, but let's say I was looking for a dozen scholars in who were interested in the same things I'm interested in:
mobile networks
virtual worlds
audio/video production
public, collaborative learning
It's unlikely that we would all work on the same research project at once, but there would be a handful of project undertaken by individuals or small groups. There would be a public face to the group and a private project management site, like Basecamp. The public face would offer a steady stream of information as we shared what we were doing, what was going on in our teaching, what we were reading and writing. We'd be assembling streams of information from our blogs, twitters, flickr, YouTube, and so on--wherever we were post information. The result is a collection of information that is hopefully useful groundwork for more formal investigation and also a mechanism for fruitful collaboration between our classes.