I don't let ANY websites show up in member profiles. All you have to do is edit profile.php and remove the line that prints the member profile. EasyPeasy, that part of the problem solved.
Also institute the other fixes like removing the member list, enable visual confirmation, disable signatures, etc.
I've considered that, but I (and several of my users) like the memberlist! I tried visual confirmation, but the one used by phpBB is so easily bypassed it's not even funny. All that did was alienate my (very few) sight-impaired users, so I took that down. People also like having their sigs.
For me, it's sort of a weighing between cutting down on spam while at the same time, not alienating the "real" users. So far it's a decent balance, but I imagine I'm going to have to get tougher as time goes along.