Fingerprints are Usernames, not Passwords
All these academic arguments about the security of fingerprints are interesting but completely are detached from the day-to-day use of TouchID.I've been using it for about a week or so now. It's incredibly convenient. It unlocks my phone almost instantly. It prevents random people near by phone from being unable to unlock it. If a thief got their hands on it, they'd have a few attempts to unlock it with a fake fingerprint, and then they'd have to enter my code. And if they fail to enter my code 10 times, the phone is wiped.All in all TouchID basically removes almost the entire burden from the security of having a locked phone. It's actually faster to unlock my phone with TouchID than codeless swipe to unlock, so it's a no-brainer to turn it on. It doesn't matter that the NSA probably has my fingerprints, in practice it prevents most people from getting into my phone in a way that is transparent and easy to use. If the spooks want my data, they can already get it.