http://armour.ws/community/memberlist.php
I have this issue. Most of my users (2,700) just register and place a link in their profile or just place in their signature. This has been recently combatted with the help of some plugins from vb.org.
It is a shame.

Would have loved it if most of those who signed up were real users. Could have at least go my forum going a bit.
I'm really considering of deleting all my users.