Earlier quoted context omitted.
Yes. If you already know someone's email address, you can get all sorts of information about them from twitter, fB, amazon wishlists...anything where the user's account is keyed to an email address.
So... isn't there something in user agreements that avoids this sort of thing? Maybe I should read it closer, but I would expect "will not sell my email address to third parties" would be a common clause. And if it wasn't, I'd expect some sort of consumer backlash. Sorry for the line of questions, this is sortof a jolt to my view of reality.
They aren't selling the email address to third parties - they are letting them access the information for free.