My opinion is that yes, it would be a Bad Thing if we could be tracked everywhere we go online, as Duncan says (side note: aren't we already!!), and it would surely be a step in the wrong direction if everybody was uni-laterally assigned an ID that we *had* to use for all sorts of services. Though such IDs (read: national ID cards) will be an inevitable part of certain government services, I suppose (but that's another story).

That said, a lot of the things we do want recognition for (be it papers, blog posts, database submissions, etc.) require identification, simple as that (the proverbial cake + eating/having it). To me, OpenID and related tech looks very attractive for many such application, as the user-centricity of it allows us to control where and how our online identity gets used. My 2 cents worth.

By the way, this stuff is further explored on a recently-launched website, if you care to have a look: http://www.gen2phen.org/researcher-identification/