Can they even ask you to do that? My understanding was searching your phone is allowed because that's treated similarly to searching your luggage. But you're not carrying your facebook or email accounts with you, so I don't see why they'd have any right whatsoever to demand to "search" your facebook/email.
Or is this something they've already started doing? And if so, what makes it legal?
Or is this something they've already started doing? And if so, what makes it legal?