This is news, in the sense that Dropbox now actively crawls your files (DMCA still went about for publicly listed files anyway).
But my question is why are there people in the tech industry still surprised by the fact that Dropbox does not encrypt it's users's files and can read them outright...
That's how they do sharing between users, as well as file deduplication (Which probably works best for larger copyrighted files, funnily enough!)
I still use Dropbox, and promote it slightly: with the stern advise to use it simply as a convenient way of sharing crap, but treat it as a "public USB drive"!
Just never, ever, store sensitive data, like your business or evil masterplans, or your personal/bank/etc account details on it. But if you're sharing that MP3 you recorded on yesterday's block party, go right ahead!