There are many privacy concerns about facial recognition.
Imagine being able to identify someone by taking their photo with your phone. What about combining that with cloud computing to determine someone's address, and date of birth? Or perhaps their Social Security Number?
Worse yet, who is already using facial recognition? What if the police were using it in conjunction with CCTV feeds to track you, or someone you know? What if criminals were instead?
There was a great piece on Spark, a radio show on the CBC that shows how technology affects our lives. I encourage you to have a listen.