While I like this idea a lot, I doubt you'd get them to agree to it. They probably think (rightly or wrongly) they'd lose too many people if the extent of their data collection was well known.
I don't think they would lose too many people, Facebook does connect families and friends in a way that provides real value to people. The people who quit Facebook this week will probably be back on Facebook in no less than 2 months and I think everyone would be more comfortable using Facebook if they can control how their personal data is collected and sold.