Pat -
Please remember that I am just a moderator, not an administrator. As I told someone the other day, my job is to follow the parade and clean up after the elephant - I never get to march in front and wear the fancy hat. From my end of the parade, I don't really know what goes on up there.
That being said, I am under the impression that we are not seeing machine bots. These are probably humans, though I have no clue why they are doing this - just for the thrill, I guess. I understand that some of them keep score, and are in competition with other like-minded idiots.
About a year ago, we went through a terrible interval where the machine bots were suddenly killing us. And it was real spam - someone was trying to sell something in every post. Chris installed a new front end to defeat machine bots, and the spam dropped to zero overnight. I don't know the details, but things were quiet until this latest invasion.
The advantage of "send us a valid email" is that once identified, the ISP can be black-listed, and nothing more from that ISP will get through. ISPs don't like this, of course, so it encourages them to crack down on the abusers.
Bobby -- thanks for the link. I'll peruse it tomorrow. Obviously I need to get a lot smarter about this issue. In the meantime, I'll just keep that shovel handy.
EDIT: OK, I just took a look at the Registration page (I know, I should have done it a long time ago), and it appears that there is a Captcha image-verification test. This is apparently what Chris installed a year ago, and I'm not sure how a bot would get past it. There is also a send-me-an-email-address block, but no indication that the address will be checked for validity and stored as a banned-ISP control measure. We'll see what the next step is.
Bill
There is a huge problem with these spammers, and the whole vbulletin community is affected. The Captcha's aren't getting them. They have valid emails, and they ARE authenticating. We do know that they're bots, and that most of them are originating from Chinese based IP addresses. What we also know is that there has been a purchase through Russia of a large block of IP's from a chinese domain. We're pushing VBulletin to make some changes, and honestly, I haven't finished reading all of the posts on the VB site, but we're working on it. There are some best known methods that we're looking at, but it also affects users signing up. There is a balance that needs to be achieved. 
