What I find weird is that when I do a google search for a specific keyword/set of keywords, I do get a lot of pictures from Pinterest. So I know there is a lot of interesting content, but I can't easily reach it FROM Pinterest.
Stolen content is a huge problem too. The problem with Pinterest and other similar sites is that most people don't even realize what's stolen; they use the site as they would be using a private space. Because I don't know either what's stolen or not, I keep my few pins private. But it has not always been possible and I think it came too late to change people's bad habits.