I've been cleaning up the member list today, to remove those nasty spam accounts. Several thousand accounts were removed.
All the accounts removed had either 0 or 1 posts and fit some additional criteria that made them look spammy. I'm pretty sure most of these were spambots.
However, a few of these were probably regular users who created 'anonymous' accounts then never used them, or perfectly innocent lurkers. Feel free to remake the accounts if that's the case.