With the current Musicbrainz system you have to specify a clientid (consisting of application name and version) when submitting puid/mbid pairs but not for submitting another data or for retrieving data from the web service.

I think this idea should be introduced for all retrieval and submission of data, but it needn't be mandatory. Might need a more sophisticated authentication method then that the current system. This would give following advantages:

1. Would be useful for Musicbrainz and Software providers to seem how much traffic their application is generating.
2. Would allow requests/submissions from an app to be blocked by Musicbrainz or because at the request of the application provider if they realised there was an issue with a particular version of their app.
3. Could enable different service level for different applications.