Mentioned shadow profiles and some other of their shady practices to an acquaintance recently, he uses fb and wanted to stay in touch using it. He chose not to listen to my critique of fb calling me a "tinfoil hat" (whatever that even means).
Still, I'm absolutely sure it's best to keep private stuff to oneself, and parties you trust. With understanding of full consequences of doing so. If one trusts Facebook, they'd better think why do they do so, as their trust may be misplaced.
I think one of problems is that when users post data they don't even think they send it to Facebook - they believe they send it to their friends there.
It's a defense mechanism.