The documentation says that each user gets 5 distinct quotas of 10,000 requests per 24 hours, and as I interpret it, per app.
If an application does have an access_token, then the application is on a distinct user/app pair daily quota (default size of 10,000). A user can have up to 5 distinct quotas at any one time, though this limit is not reflected in quota_remaining returns for privacy reasons.
How is the quota managed if the user has more than 5 apps using access tokens? will 2 of the apps share one 10,000 block? or can the user only use 5 apps (that use access tokens) at once?
Basically should I expect the possibility of having no quota to use, because the user already has 5 apps?