From an ease-of-use POV, it would be much nicer if libcloud had a concept of session, and with that enough state to store credentials for each backend.
Yah, I think I agree on that. I'm working on a write-up about sessions and auth, again.
For a service that exposes the libcloud API though that storage must be persistent, and not just in memory: otherwise users of the API will get very strange errors when the service is restarted in the middle of one of their sessions. Basically, they'd have to expect a 'sorry, forgot your credentials' error on every API call, and then login again and redo the call.
I think they have to expect *some error* is possible at any time. It might be a 404 Not Found while the service is actually restarting, even if the service does maintain a persistent store of sessions. I think this QoS is more a function of an implementation. You could use ∂-API services without persistence, as long as you're aware of it.
-Bob