Isn't this why, oh, around 2005 CPA was the big thing instead of CPC? Personally, I think CPA is absolutely the right way to do internet advertising, and I wonder why FB doesn't do that.
Most sales or acquisitions originated online are based on rational decisions, not on the appeal of annoying ads.
The day advertisers start to use a verifiable CPA system, 80% of online advertising cease to exist and 95% of today's start-ups see their cash vaporize.