The theoretical computer science community has a pretty active blogosphere that indeed “carries a conversation” for the field. Lance Fortnow’s Computational Complexity blog (now co-written by Bill Gasarch) has been running since 2002. Luca Trevisan’s blog is focused on complexity, Scott Aaronson’s on quantum computation, Michael Mitzenmacher’s is general, Richard Lipton’s has an historical point of view, and they all, as well as a few others, are really interacting with each other to a level that gives a feeling of a community [Added after a well desrved snark at me: Suresh Venkatasubramanian's (and a few other) focuses on computational geometry, and Mihai Pătraşcu's on data structures.] I think that this mode of community-building is good for science and we are yet exploring the possibilities. (In this vein, it’s hard not to mention the recent spectacular polymath project on Gowers’s blog.)
Part of the motivation for this blog is a desire for the creation of a similar community for algorithmic game theory. Some blogs in this community do exist: Muthu’s, Paul Goldberg’s, and David Penock’s is also related. Lance also writes on AGT stuff in his complexity blog. A community is in the making and I want to be part of it.