Forum Spammer(s) and Bots

I've never seen anything like the spammers and spam bots that actively attack forums creating new accounts.

I guess I can understand why it happens, but why aren't they stopped from a global scope rather than each and every forum admin having to put in measures to try and stop them?

HostGator could simply block the IP's and prevent all accounts with forums from having to battle this problem. I promise it would be a great selling point.

Alice