If you take a look at the member list, you'll notice that out of just over 2000 members, 642 of them have not posted at all, and quite a few haven't logged on since they registered. Then there are loads more with less than 5 posts. It probably is annoying when you register, to have register form tell you that your name is already in use by someone who never posted. So I propose this: Members that have not logged in for six months (or some other length of time), and have 5 (or some other number) or less posts, should be deleted.
The terms might be changed, you could warn them, but I think it would help let new members have a name they wanted, not some odd thing as a last resort.