I contribute from time to time to OSM. What bothers me a bit is my productivity when doing surveys with my phone and OSMTracker. The GPS is not precise enough to record doors locations precisely, and taking photos is time consuming (I feel quite productive when tracing roads against satellite views using JOSM, though). I can imagine that Google's stack (with their Google cars and adapted home-grown software) must be something like 100 or 1000 times more productive.

Also, OpenStreetMap provides the data, but Google aggregates the data, which makes very cheap to add/search a lot of information (ex: shops) available from on-line sources (such as web sites). I don't expect OSM to have the same amount of information any time soon.