You're basically asking to show ads that are even more irrelevant and useless to your users?

The best ads for publishers and users are ones that are relevant. If you want to display something that is irrelevant to the user and ineffective for the advertiser, you might as well not display ads at all and avoid annoying your users.

Through our marketplace we don't track any personal or sensitive info about users, or use it to figure out which ads to display. The most sensitive info we use to show ads would be geo-location (just country...). Advertisers are selecting the sites they want to advertise with based on the sites topical area vs. us coming up with some magical algorithm that matches an ad with a user.

You mean doesn't track views but only tracks clicks/conversions?

The only problem I would see with that is that if a user already converted by clicking the ad, he would continue to see the same ad when he is on your site again. You're no longer able to extract more $ from that user.

If you're wanting that, host ad banners locally and use CPA/affiliate links instead. The additional benefit to this is that Adblock doesn't block them unless you name the div id or url 'advertisement'.