or a group of hackers to figure out how to collect the fingerprings of EVERYBODY who owns a smartphone with fingerprint scanning.    how hard can it really be?   all the fingerprints are saved on the phone.  the phone is connected to the internet.  the internet is connected to Russia or China.  It's only a matter of time.  
 
  
worse yet, perhaps the NSA has already implemented this and is actively collecting fingerprints around the world.   one scenario... they have the fingerprint of some terrorist.   the NSA matches  the fingerprint to its database of fingerprints secretly collected from ALL smartphones in the world.  the location of the terrorist can be easily identified within seconds.  (another half hour to send a drone to his/her house?)  
Tin foil hat off. 
