Considering that people generally don't wear gloves when they use their phones this is like having a picture of your key on your door. Combine that with what we know you can do with pictures of keys[1] and yes it's obviously not a very good idea.
This is not being done by lifting an existing print from the existing device. They're taking a photo of the authorised FINGER and using that to create their fake finger...
I don't see how this could be considered a significant issue unless you are going to steal someones phone AND somehow get a still 2400 dpi photo of the surface of their finger
If the print was copied directly from one of the phone surfaces, you'd think that the CCC would want to include that little tidbit.
That brings up another interesting point -- I wonder how many people are going to put screen protectors on their 5S's that are not oleophobic.
Does that mean you couldn't find my prints in other places? Sure. But I can probably find your keys in other places, too.
We know that SSL is generally not implemented properly, that the CAs are probably all hacked or subverted by the NSA, that the NSA may have developed backdoors to a number of the more popular encryption suites, but I don't hear anyone running around demanding Google or Facebook disable SSL.
If you are doing something that requires sufficient security that you don't want someone to access it via your fingerprint alone, add additional layers of security.
If you are doing something potentially incriminating ... don't do it on your freaking phone because it's probably been exploited in a dozen other ways by various authorities who can use it to find out most of what they need without being in physical possession of the phone anyway.
Most people aren't worried about the mafia or the CIA or the NSA. Most people don't even bother using a passcode, let alone a passphrase on their phones. If you can add something as easy to use as this, then it adds an additional layer of security against the casual abuse most people will find themselves subjected to (random people making calls from your phone, spouses spying on their email, etc.).
If you are worried about the CIA and the NSA, using a phone at all for anything is probably not in your best interest at this point.
CCC made it look easy but I bet it didn't work for them first try or even 5th try...
Yeah, but as every decent locksmith will attest, very-nearly-almost-all door locks can be easily opened with the right tools. Like picking a lock is a specialist skill, so is lifting a fingerprint and making a copy of it. No security is absolute; it's all trade-offs. Making it such that it's not worth your adversary's time to bother.
And that is what happens with a finger-print based secure system; you inadvertently place the imprint of the key on the phone's display as well as public places.