I don't think Sandstorm wants to be a platform on which you host your large user-facing app. Instead it wants to be the platform on which you can install your personal wiki, ipython notebooks, your streaming media library, etc.

You as the owner of the Sandstorm instance will control whether the apps on your instance can send data to Google for Google Analytics, for example.

If you invite someone else to use an app on your Sandstorm instance, they will trust _you_ with their data and you can decide whether the apps on your instance share the data with Google or not.