I think solving this problem is just a band-aid. As sites like Facebook and Twitter have become mainstream privacy concerns are also becoming mainstream. We're going to have to develop better ways of working with people's data -- kind of like PCI compliance but for personal data. I'm no fan of regulation, just making a prediction.

That said, if you don't need access to someone's entire social graph and just need an email, you should just ask for an email. Let's at least start there. But when the only business model anyone seems to know is "collect metric tons of data and sell it to advertisers" I'm probably yelling into the void.

Edit: err...oops. That probably sounded a bit spammy based on the down votes. Suffice it to say I'm starting a nonprofit in this vein. Info is in my profile.