At my bodega down the block, photos of shoplifters sometimes litter the windows, a warning to would-be thieves that they're being watched.

Those unofficial wanted posters come and go, as incidents fade from the owner's memory.

But with facial recognition, getting caught in one store could mean a digital record of your face is shared across the country. Stores are already using the technology for security purposes and can share that data — meaning that if one store considers you a threat, every business in that network could come to the same conclusion.

One mistake could mean never being able to shop again.

While that may be good news for shopkeepers, it raises concerns about potential overreach. It's just one example of how facial recognition straddles the line between being a force for good and being a possible violation of personal privacy. Privacy advocates fear that regulations can't keep up with the technology — found everywhere from your phone to selfie stations — leading to devastating consequences.