I think we should have another of those questions while registering, like 5 or more of them.
For example, after typing in the captcha people have to answer a random question, might be "what are the last four letters of the domain?" or "most visited website in the world?", just random thing that aren't too hard to find if someone puts in 3 seconds of thought.
I don't know if it's installed but there's a plugin that requires javascript to be installed while registering and I've noticed on my forum that it does keep a lot out.
The bot problem has been pretty bad compared to normal over the past few days. Usually more than 3 an hour. And these are simply just the ones who post. There are even more bots who don't post.