Systems that don't deal well with edge cases aren't so great.

For people who don't really need to care about privacy, I guess that differential privacy is good enough. But there's a gotcha there, for people who ought to care, but are clueless. I'm reminded of that ex cop in Philadelphia, who believed Freenet's claims about plausible deniability.

Edit: A prudent standard for calling something "[foo] privacy" is arguably PGP.