vincevincevince - 5:47 pm on Feb 17, 2007 (gmt 0)

I think that the situation here is gray - neither black nor white. If you are the blogger then you can clarify the situation by:
a) Only running the ad if you truly believe it would still be put there without payment, or:
b) Adding rel=nofollow to the link to show that you are providing a link for your users but you are not saying anything about the site itself