You borrow someone's phone? Have people forgotten how to talk and help each other? It is very rare for phones to get stolen or break down, and when they do it is a lot easier to borrow a phone to pay for a Taxi than it is to beg for the money for a Taxi ride, so the situation still seems better than what we had before.

Main thing stopping this would be that most phone OS doesn't seem to support guest logins, but that is an easy technicality to fix as long as there is demand for it which there will be as phones becomes more important.