[wacheena]

In my experience modern ad systems use, among other things, CPC x CTR. Using CPR x CTR is good for all stakeholders: 1. Advertiser value - the better/well targeted the ad, the lower the cost 2. Publisher value - higher CTR means more clicks, means more $$$. 3. And most importantly, user value - higher CTR is generally a good indicator of better targeted ads

[entrepreneurial]

Really good points. Thanks for the feedback. You still have to layout money before you make any, hence the reason why the groupon model is so enticing from an advertiser's perspective.