There are two things that worry me about this post:
- that people think that they can change a contract just by saying something that the other party most likely never even read, which to me is like thinking that McDonalds will pay you $1000/hr to flip burgers just because you told your friends you'd like that wage
- that there seems to be no distinction between what is legal and what is enforceable. It doesn't really matter if what Facebook does in relation to user rights is legal or not, whether or not there is a pragmatically enforceable breach does. If Facebook did use their data in some way that the message forbids, how do these people think they're going to stop them? By showing them a wall post? At best it's going to be weeks of stress and/or thousands of dollars.
It's the same as if a bootstrapped startup has tried to defend their product with a patent. Sure you have a legal right, but how the hell are you going to enforce it if Google decide they want in?
Also: preventing citizens from contracting out of their legal rights would actually be a huge violation of the citizens rights and runs against the underlying principle of contract law in most jurisdictions - that two parties who've made an agreement freely should be bound be that agreement.
There is an assumption that you've read the terms and conditions when you signed up for Facebook and they don't really hide the fact that everything you do is more or less theirs. I don't really think you could say that you're induced into anything on it. You might get lucky in the right court with the right advocate, you might not.