Seems that there would be quite a bit of historical value to getting everyone to digitize their personal photos and upload them to a shared repository. Has there already been such an effort?
Unfortunately trying to construct street level from this technique would be difficult as people would have to manually geolocate to an extent, which would generally grow the older the photos are. But I think sites like Mapillary and OpenStreetCam don't have a required freshness of photos, though I've found by accident Mapillary has a minimum at 1 epoch time.