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.
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.