Good thread. Some useful info there. I constantly have things trying to shove their ads into my guestbook. None make it in with the validation I do now.. for awhile if I detected a bot, I would respond with a location header back to themselves. Now, I just respond with nothing.
I even have things trying to access non-existant guestbook scripts. dumb bots... anyway I can only really block IP addresses of constant offenders since I get a lot of ligit hits from overseas downloading my midi files.
I do however, blacklist everything from overseas in my email client.. *
*.??