Originally Posted by tore

Possibly, getting rid of bots is a tremendously hard task, but I was able to do so quite easily on my own forum by having questions that have to be answered correctly in the registration form.

It's a Canterbury forum so I just used some simple Canterbury-related questions. I figure it should be easy enough to get the same for this forum - just some questions that any musically interested person can answer but which a bot can't. That security function is integrated in phpbb3 (free forum software) so I'm sure it can be added to vbulletin if the functionality is not already there. Perhaps even questions like "what is eleven plus six?" or "what are the 7 first letters of the alphabet?" would be good enough to keep bots from registering.