Disclaimer: lead developer of Trovebox / OpenPhoto
I wish more folks would make this distinction. Going one step farther I set out to create a layer on top of Dropbox that was optimized for photos (and videos).
Essentially, give a proper photo API to the files in your Dropbox. Things like date searches, plotting photos on a map, etc.
Then another step beyond that. Migrate between any storage service without losing a single feature, keeping every URL in tact and a mobile app which continues to work as if nothing happened. Dropbox is great but it isn't future proof either.
Then the last (and probably most important) open source it all.