When someone visits one of those links, they are presented with a unique challenge and response system to ensure they are "human".
When the user chooses the correct box, they get your email address:
If you made a mistake during code selection, you get a box like this:
If for some reason the above box selection doesn't work, the user can click on the link entitled "Try the failsafe captcha mode" and enter the code in the usual Captcha method.
Not sure this is something I would use but some of you may find it interesting.