This does not exist yet, but I've been thinking about it for a long time. I think we generally need to move away from a centralized cloud to a more distributed cloud, where you can host your own applications on your own server, encrypt and protect them as you like, and share them with whomever you need via a secure API. You can imagine having a photo app, a social networking app, video sharing apps, document apps, whatever people can build and deploy.

You'd need standards. Standard web service APIs, standard authentication, standard privacy controls, standard database layer, standard encryption between nodes. And that would take most of the effort off the individual apps for handling all this. They'd just say "I have this chunk of data, and it's accessible to these people" and if the everything checks out, the app can grab it from whatever node it's on.

There needs to be this sort of operating-system-for-the-web on which people can build distributed apps. Something like Diaspora is trying to be, but without the limited social networking overtones. A platform where security, privacy, distributed social networking, and sharing are the main concerns, and the apps built on top of it more general.

It might be interesting. I've had this idea since about 2001 but never got around to building something. Maybe it's the right time...