It also doesn't mean that there is a massive inefficiency created by a large number of users ignoring a large number of ads.

I'm not sure how you came to this conclusion, or what constitutes a large number. I'm not saying your wrong exactly, but it sounds like some pretty significant assumptions are being made in your statement. Proof?

I was actually under the impression that most people find the ads relevant more often that not. However, I can't remember where I read that so I won't stand behind it.