I Hate My Cubicle!!! had a post about BlogLinker.com, which is a blog linking service. The way that it works is that you add web sites to your url list. Then, in addition to that url appearing in your list, your url will appear in their list, if they have also signed up with BlogLinker.
This is an interesting way to get traffic to your website.
Looking on the BlogLinker website, it looks like spammers have used this to spread their urls. I think that this is still a possibility, since there really wasn't any verification of my information when I signed up.
At least you can configure BlogLinker to automatically hide new links. And you do get emails when someone adds you to their list.