To me, this is akin to Navajos believing cameras could steal their souls.
Let's pretend for a moment being on Facebook really did set you up for identity theft. In this reality, eventually, we'd all have our identities stolen. This could teach us a valuable lesson. Maybe we'd come to realize these identities we hold so dear aren't really something we can "own," and that we are too attached to our idea of "self."
But what's so bad about a future where I steal a little piece of your identity? After all, in this world, you've probably pick-pocketed a little slice of mine. My neighbor downstairs might have stashed away some of my identity too. He's probably after those precious years where I had all my hair and zero acne. In the end, we'd all own a little piece of each other. Isn't that beautiful? Our true connectedness would surface and we'd all become One.
I'm ready. I'll get the ball rolling. My Social Security number is 105-75-63... On second thought.