The problem is that wordpress.org users who want to use Akismet (which is bundled with 2.0.whatever) have to sign up here to get their API key, and get given a blog whether they want one or not. I said from the outset that this would unnecessarily crowd the namespace and people would start getting annoyed because their desired username had been snaffled by somebody who had no interest in using it. It would be interesting to see what proportion of the '146 thousand blogs' advertised on the home page are actually active.
Of course, the problem with notifying blog owners that their account may be deleted is that they may no longer be using their sign-up email address. Also, there's no mechanism for releasing deleted usernames for re-registration (this has caused problems for people who delete their blog on impulse then find their username has gone forever). On the whole, I think the attitude of the developers is that not being able to get the username you want 'proves' how popular their service is, so I'd be surprised if any of these recycling suggestions are taken up.