Er, what? Every single site I can think of 'leaks' this information through their registration page. Try and sign up for a new Scribd account with an existing

Er, what? Every single site I can think of 'leaks' this information through their registration page. Try and sign up for a new Scribd account with an existing email: "That email address is already taken; please choose another one" Try to sign up for a Facebook account with an existing email: "Sorry, it looks like somebody@somewhere.com belongs to an existing account"