This is quite misleading. Before Graph Search much of that capability was limited to Facebook Inc. and the affiliated government. This really opens the floodgates.
Were they warned? If you follow Wired and HackerNews yes. For general population though it's not something they were warned enough. They teach you how to cross a road in elementary; nobody explains you how to use privacy controls.
The whole liking and sharing ecosystem is promoted by social media itself. While you have skills to be critical of privacy implications, many more people have very vague idea or none whatsoever. Facebook de-facto is seen as a way of communicating with your social circle, that's why normal people join it; there is a (misguided) expectation of the same kind of privacy that you have in a clique of friends.