The problem is this: What if I don't have an account, but somebody still happens to tag my face with my name, for whatever reason?
I know that this is mostly about facebook users, but seeing how much facebook spam I get trying to incite me to join in, I could totally see them go this route - Encourage people to tag friends who aren't on facebook and thus give those friends no other choice but to claim their identity.
I'm only talking about faces tagged with an actual Facebook account.
It's unlikely they would enable facial recognition for non-Facebook users. How will they know the difference between two different people tagged as "John Doe" if they're not linked to a specific account?
By their faces! Also gender, location, preferences, web pages visited (they still track your browser even if you don't have a profile), and by the networks of people who talk about them.
This already happens. When someone goes to your neighbors and asks around about you, your neighbors probably spill everything they know about you immediately. (If not immediately, a little story about an "ongoing investigation" should push them over the edge.) It's going to work the same way on the Internet. It's a little scary, but I prefer to think about the good applications rather than the bad applications. Having realtime facial recognition at conferences, for example, would make my life a lot easier.
I know that this is mostly about facebook users, but seeing how much facebook spam I get trying to incite me to join in, I could totally see them go this route - Encourage people to tag friends who aren't on facebook and thus give those friends no other choice but to claim their identity.