In You Are Not a Username, Jason Kolb suggests that the blogosphere is really just a large, losely-coupled social network, and that your identity on that network is your blog’s URL, not a username.
I think this is an area that needs to be explored further because I really don’t like the concept of having a separate account at every site I belong to. It really should revolve around my personal Web site, wherever that may be, and that should be the end of it. It’s a simple matter of relabeling the blogosphere as a social network and layering some existing technology on top of it to add some more value.
This sounds very much like the type of thing you can do with OpenID. For instance, using the OpenID Comments for WordPress plugin, your blog becomes an OpenID server, and you can identify yourself on other OpenID-enabled sites simply by specifying your blog’s URI as the OpenID provider.