Hi Mike, I've been getting the same thing on my site. Offers from people wanting to SEO my site.

There is little you can do about it, because it falls in to one of two reasons:

1) They have spam bots that get others to solve CAPTCHAs. They take the CAPTCHA your site displays and sends it to a computer that has a virus on it. The box pops up saying "Enter in the code within 3 minutes (the timeout limit for some CAPTCHAs) or your PC will shut down". The person panics, fills out the boxes and the results are fed into your submission form, therefore solving the CAPTCHA. See http://labs.m86security.com/2009/08/koobface-malware-distribution-t... for an overview of how this happens.

2) They have people doing this by hand. If they get a commission each time you click on the spam / sign up for their service, they will post their message anywhere they can in order to make some extra dollars.

You can blacklist sites in C5 by going to your dashboard and clicking "Sitewide Settings > Access" and fill out whichever box suits your needs. Problem is, if they're from bots, they could be all over the world and blocking them may block a shared IP address or a person wanting to view your site.

Hope this helps!