This is both a general WordPress question and plugin specific.
I'm wondering about using this plugin for serving documents more generally, as a replacement for 3rd party cloud storage where security is universally weak to non-existent.
So have you considered supporting encryption of documents on upload (on the client)?
Groupworking with this level of security would I think make it into an outstanding "must-have" product when people begin to realise how vulnerable their data is in the cloud. Currently there is too much ignorance over these issues, but that will change when bad things start to happen, which is inevitable!
Mark (in London)