Seems to me that 1 user can store their data in 1 or N local or remote silos. classically each local app had its own data store, so 1:N. Web apps were the same except that each of the N providers could monetize your data and lock you out. Google and FB are using SSO to abstract the N behind one front door but really thats just so they can monetize the data instead of the N vendors.
Having 1:N but the user controlling where those N are stored, and that storage being portable between backends, seems like the right choice. Bonus points if apps can share data between themselves M:N style, although that is fearsomely hard to secure (exhibit A: windows registry).
A localized database stored in a non proprietary single file format that can be moved around and rsynced, dropboxed etc at will, plus a common, network independent access protocol so that open/read/write semantics work whether the thing is local, at a URL, etc just work would seem to be very desirable and possible with todays tech.
Having 1:N but the user controlling where those N are stored, and that storage being portable between backends, seems like the right choice. Bonus points if apps can share data between themselves M:N style, although that is fearsomely hard to secure (exhibit A: windows registry).
A localized database stored in a non proprietary single file format that can be moved around and rsynced, dropboxed etc at will, plus a common, network independent access protocol so that open/read/write semantics work whether the thing is local, at a URL, etc just work would seem to be very desirable and possible with todays tech.