I disagree, I think the situation you're talking about sounds like the classical napster/kazaa/bitorrent kid with a ton of songs on their hard drive who is ripe for legal action, whereas the pinterest situation -- even in a worst-case martial-law scenario -- is more like you've streamed a movie to your hard drive from Youku or something like that.

The end user, when they don't have anything sitting in their house, is much less liable to be prosecuted.