For instance, you could have a fire-and-forget self-service self-provisioning online shopping site builder, and bill database costs through to your customers (we give you that information in response headers).
You can also use FaunaDB to do consistent coordination between FaaS execution environments running in different clouds. So if you like a processing feature Azure makes available, but want to run your user facing servers in GCE, you can use FaunaDB to coordinate between the clouds.