I like the site and concept. My 2cents: Some of the graphics need tweeked - like the go button and the hot callout bubble are a little cheesy. I am guessing the ad creator/publisher will be able to choose the border color - so I won't go there. Will the advertisers be able to create Flash ads? I agree with mixmax; I think the ads should be relevant to the content of the site. I noticed that your the only founder; since you know what your doing from a programming point of view, I'd look for a co-founder who has a design background. Once again I like what you are doing.