What should be the mechanism for login in a shared smartphone or tablet? Should it be username + password as it is in PCs or should be enough using a password / PIN?
I'm interested on both security and UX but mostly in the balanced tradeoff between both of them.
EDIT: I'm thinking about the concept (not an actual product) of a shared device (same as shared workstation).
Scenario 1: A company has a pool device with data (mostly) in the cloud and decides to control who access the device.
Shall go to traditional username + password login or is there something else that can be done? Of course username / password would work but trying to improve UX (simplify).