I understand those, but many of these are pure SPAM nonsense and are not even promoting sites. But I think you've answered my question so thanks.

I approve all of my new registrations, and I really haven't had a spam problem. Doing the approvals is a pain in the neck, though. I run the emails through Google, and any hits from stopforumspam will usually show up there. In many cases, you can see other forums that they belong to, and whether they are legit or not. Suspicious IP addresses are run through stopforumspam directly. I find a few, but not all that many. I'm getting probably 300 new registrations per month, so it is very time consuming for me, and frustrating for the new registrants who want to be posting.

On the registration page Rick needs to add a "human question module", CAPTCHA will not help, when we enabled the human questions available in later versions of vB it stopped all the Xrumer bots from registering.

I beg to differ, the CAPTCHA brought our automated spam posts from about 90 per day to may be 2 per week (and I'm pretty sure those are users paid to register and spam vs bots).