changes a file in a way you don't like. You shouldn't share a file you don't want messed with, and that's what this clause covers. The things that a person might do with a file when you've shared it with them is "use, copy, distribute, prepare derivative works (such as translations or format conversions) of, perform, or publicly display" it. This is true of any shared file on any shared drive anywhere, but because the file is controlled by a third-part, for-profit entity, they need to make that explicit. "to the extent reasonably necessary for the Service": This is also new to the clause, along with the sentence you've mentioned. This I read as the part where they're saying they won't use your stuff themselves. It is not reasonably necessary for Dropbox to sell works of art or use files in advertising, so such uses would violate this clause. I think it still could use some work, but that's how I read it. "You must ensure you have the rights": Again, this I read as related to sharing, not to how Dropbox will steal your stuff. I have (or at least I think I have) the right to use Dropbox to share a copyrighted file (an e-book, say) with myself across computers. I do not have the right to share that book with others or drop it into a Public folder, thus if I am caught doing so, I can be suspended for violating the TOS. The latest episode of