We use a similar method at Facebook. http://www.facebook.com/note.php?note_id=10150212498738920 http://www.facebook.com/note.php?note_id=10150212498738920 If

We use a similar method at Facebook. http://www.facebook.com/note.php?note_id=10150212498738920 http://www.facebook.com/note.php?note_id=10150212498738920 If I had to guess, I'd say that since route 53 is a dns host for many domains, they might be able to work out the user ip / resolvers map passively. Pretty awesome stuff, Amazon! This is a big deal for your customers.