hugh - 9:13 pm on Jan 11, 2011 (gmt 0)
Not recently. I had to disable a StopForumSpam mod on my forum because it stopped working. Tons of bots were registering and the IPs and usernames were not in their database.
I switched to a random Q&A to keep the bots out - the only spammers who have gotten in was a guy with two accounts who dropped a tag-team "question" and "answer (with link)".
A mix of plain english questions, StopForumSpam, Akismet and human moderation works very well for me...