I'm working on an app that focuses on displaying Google Streetview photo-spheres. I'm using v=3.exp in my app. Until yesterday, about 90% of the photo-spheres I would routinely view by going to a random LatLng and finding the nearest photo-sphere were NOT photographed by Google Inc but by individuals. Which I like very much. Now, all of a sudden, I can't view any of such panoramas, only ones photographed by Google. What gives?
Google is working on adding new functionality (StreetViewSource) to the API, it is possible that things are not yet working correctly. That new functionality is not yet documented in the Developers' Guide (at least that I can find today) so it is hard to say how it is expected to work.
There was a request to not return indoor panorama's when not desired that has been recently marked as "fixed".
Not sure what version of the API you are requesting, but the "experimental" release (currently v=3.21) is just that, experimental, it may break at any time. If you don't see the same issue with the "release" version (currently v=3.20), you may want to file an bug report as v3.21 will eventually become the release version (according to this post, August 18th...).