"Dropbox it's not a product, it's a feature". Don't get me wrong, I'm a Dropbox user myself, but I don't see their actual moat. Isn't cloud storage a commodity nowadays? IMHO they should have spent money in investing in other productivity companies in order to diversify and be able to offer a complete productivity suite.
It's easy (trivial) for a technically proficient person to setup any trivial cloud storage system they like on just about any provider's platform they like.
It's not so easy for anybody else (read: the vast majority of other users). Dropbox's value proposition isn't commodity storage on somebody else's servers: it's the UI/UX that backs it, and the particular implementation details.