WallyWorld - 12:47 am on Dec 7, 2005 (gmt 0)
There is no guarantee that anyone clicking on the link will advertise on your site. They can just as easily advertise on any other AdSense site or none at all. Either way, it takes the visitor away from your site without any monitary gain. It also makes the ads seem somewhat cheaper with that offer and I think distracts possible other clicks. My stats (and others stats) seem to bear that out.