"Robert Scoble, as far as I recall, was trying to download all his contacts and all their information out of Facebook. And this is a little bit different to what we're doing."

Trust me, Facebook doesn't care. Having me giving your credentials and then logging in on my behalf will get me banned.

"However, Facebook is not the only one network that we target to."

No, but here's a question: of your target audience what percentage have a Facebook account?

Not that it matters. Most social sites (or the smart ones, at least) have a policy against automation. LinkedIn stopped NotchUp using the same rationale, for example.

Can you be forthright? Let's say I sign up to your site and give you my Facebook and LinkedIn credentials. What, exactly, are you going to do with that information?

If I delete my account will all of my information on your servers be deleted? Will you ever send me notifications -- whether via email, IM, InMail, Facebook message, or whatever else -- that contain advertisements targeted based on the data I handed over to you?