Quite honestly this is not a major concern for us. People can always choose different user names, and if not being able to take the name they prefer prevents them from signing up, somehow I doubt they would be likely to be active contributors.
As for the bandwidth? Minimal.
Ultimately it's more of a hassle to remove "dead" accounts than it is to just leave them. Determining by automation whose account deserves deletion seems very prone to error, and doing it manually is far too time consuming to be justifiable.
- Oshyan
