If anyone attacks those IPs its going to result in some poor stupid user that has some malware on their machine getting attacked and saying "OMG@random hacker attacks!**!"
The best defense against forum spam bots is to delete them and NOT to visit the addresses they link to. Ignoring and removing them is the ideal approach because even spam costs ***** and if nothing is gained by spamming (site traffic/rankings/sales) then spamming will become a waste of ***** and therefore stop.
Thats my opinion on the matter. All you need are a few good trusted mods with topic deletion or at least profile edit ability... but being these forums are no longer regulated Id call it a lost cause overall for these forums at least.
edit:
As far as the parents sueing for minors being exposed to porn I hate to tell you this but its not the sites responsibility for user based content and that lawsuit would fail... and fail miserably. If that were the case I could use my kids as lawsuit machines and go post a pic of some boobs on a yahoo profile then sue yahoo cause my kids saw it, and do the same with AOL, MSN, myspace, facebook, every free hosting service on the net, every paid hosting service on the net... come to think of it anywhere anyone can post anything, including avatars, photbucket, imageshack and anything else.
As far as the pharmaceuticals go, as long as people BUY them they will find loopholes to SELL them.
***** talks. the more you have the louder it talks.
thats just the way it is.