can't and won't are effectively the same thing in this context; you're picking nits about free will.

Yes, of course everyone can always leave. The only price - for more than a few of those 2 billion - is the complete disruption of their social lives. Telling someone they can never see cute pics of their lil cousin again is punishment, not a serious decision about consumer responsibility.

You can tell because a history of malfeasance and yet, 2 billion active users.