Facebook picture labeling

I want to train a neural network and use open CV for facial recognition. Nicholas Martin, whose a user here on SE told me that this is a supervised learning class (clearly). So I need pictures and corresponding labels. So I thought hey! Maybe Facebook could be of help. So how can I label potentially millions of facebook pictures? Would it be by the user's profile name or is there a way to find out the name of the person by some scraping method? How would it work? I'm guessing it will only be possible with users who accounts are not private