This is, as far as I know, already in the Dropbox T&C's (article here http://articles.businessinsider.com/2011-04-18/tech/30033770_1_user-files-user-data-law-en

This is, as far as I know, already in the Dropbox T&C's (article here http://articles.businessinsider.com/2011-04-18/tech/30033770_1_user-files-user-data-law-enforcement http://articles.businessinsider.com/2011-04-18/tech/30033770...) and their T&C's here https://www.dropbox.com/privacy https://www.dropbox.com/privacy do mention handing over data in relation to law enforcement requests in section 3