That's no kind of evidence. There is at least one hidden premise to your argument, something like "If people cared about their privacy, they wouldn't use Facebo

That's no kind of evidence. There is at least one hidden premise to your argument, something like "If people cared about their privacy, they wouldn't use Facebook et al", which doesn't seem true to me at all. You first need evidence for that. But these points have been debated a thousand times on HN already... (Anecdatally, I hate that such sites sell peoples' information, but I use FB)