OK, now you're being just silly. Security wise, there is an extremely low probability that you would obtain someone's phone AND obtain their fingerprint at the same point in time. We're talking about a stranger obtaining your phone or thief; not your friends.
Even if you found/stoled the phone, managed to somehow track down the owner to get a fingerprint, enough time would have elapsed for the phone to have been reported stolen and is basically useless.
i dont disagree that its an extra hurdle to someone getting in your phone, but having physical access to the phone is the biggest hurdle,not the fingerprint,and not the passcode. actually,cloning the print might be even easier than getting the passcode in certain cases.
i was under the impression that the discussion is about the security of the fingerprint scanner,which apple is touting as more secure,which has been proven to be not secure at all,and can easily be broken. making your phone physically available to other parties is something totally different. unfortunately, no phone manufacturer has a feature that prevents stupidity.