Store custom data at the user (like an mdb in the users own filesystem)
I like to be able to provide custom data storage - inside the users own office365 - for the users of my applications, like https://www.dropbox.com/developers/datastore .
With that I would be able to create applications without the need to provide and maintain a data backend. And the user would not need to rely on (or trust) a database maintained by me.
With an easy to use api (like azure mobile services).
Jonas Eriksson commented
The problem with azure mobile services is that the db is still owned and maintained by me. I like the users to be able to disconnect from my application / service whenever they like, and still keep their data.