[ma2rten]

Accuracy depends on the dataset like you point out. It's a hard task to find a person among all driver license photos in the US.

[sunebeck]

Anecdotally, FindFace found my Russian friend's VK.com profile (amongst many millions of such profiles) as the number one hit after I took a picture of her in a bar and submitted it to their face recognition service.

[digsy]

I think your example is different to this scenario as your friend will have submitted many pics to VK so they have decent training set for her face.

Whereas the DMV only has 1 picture of a suspect so it will result in more false positives.