IMO it's not reasonable at all. It might be boring but it doesn't take much time at all and forcing your users to login with facebook is just lazy and irrespons

IMO it's not reasonable at all. It might be boring but it doesn't take much time at all and forcing your users to login with facebook is just lazy and irresponsible. A social experience might be nice but make sure it's optional, having only facebook as a means to login makes you look fraudulent.