Disclosure - I work on Harp

In order to build a truly compelling service that solved our problems, along with others was to allow collaboration and sharing. Right now Dropbox has no way to share within sandbox style applications.

We have been talking with Dropbox about ways to improve their API and things are only getting better.

Right now we maintain the NodeJS API[1][2] and have sandboxing build in at that layer, so we don't even see any files from Dropbox outside of the folder we have scoped to.

[1] github.com/sintaxi/node-dbox [2] https://www.dropbox.com/developers/core/sdks/other