Jon, call them whatever you want; hu-bots or spam-bots or magical leprechaun-bots. The fact remains, spammers do indeed continue to post in this forum where they do not in other YaBB forums that use proven anti-spam measures to stop them.
By the way, I agree with you that it's unacceptable for a forum to ask questions that only people with a specialized knowledge can successfully answer.
To that point, just to better identify if hu-bots or spam bots were registering in our forum, I actually included answers with the questions I asked, and I explained this to registrants.
I'm using a different method of spam control now, but for a while we had the following alternating questions on the registration page of our forum:
Quote:To help stop spam-bots, please answer this question: What is 1 + 1 (the answer is 2)?
To help stop spam-bots, please answer this question: What is 2 + 2 (the answer is 4)?
Can a hu-bot answer these questions with the answers provided? Of course they can, which is why it was determined that except on the rarest of occassions, only spam-bots were making attempts to register in our forum.
Silly, silly, silly, but it did make me laugh.

Oh, and if you think spammers haven't been able to post spam links in this forum, you haven't been around to see that it happens. They simply post a dozen or so times all over the place to accomplish this task. Thankfully, YaBB's moderators have zapped them away in a timely fashion.
Meanwhile, new members who come here for help are unable to post links as they may need to do. Then again, at least they're able to request help right after they've registered, and that's what counts.
Hopefully we can agree on at least one thing about spam in this forum. That is, it doesn't happen that often, and when it does, YaBB's moderators are pretty quick to get rid of it.