The tradeoff sounds scaring: - Extremely accurate Privacy Policies nobody read; - Simplified Privacy Policies everybody read, but missing something.

Facebook has probably reasons for not including too much detail on that page, but Facebook also uses users' data like nobody else. For the average website this problem is much simpler, even for the average SaaS startup which is not a social network (or a simple one like Quora). Probably that kind of website can really have a privacy policy covering every personal data use within a simplified popup, without missing relevant information.

The Facebook's popup surely has issues, but I still love it since it's something people read, and it helps people take better choices. This is what, to me, is really important of Privacy Policies.