Well, at least Strava now has a global heatmap: http://labs.strava.com/heatmap. Makes it easier to avoid roads less travelled, I guess.
Regarding the data quality: At least in Germany the ADFC maintains its own cycle path network which also contains metadata about road surface, motor traffic and such things. This is also one of the sources Google licensed for their bike stuff in Maps (although back when they introduced it they had a very hard time matching up their two or three different data sets and there were lots of errors where junctions wouldn't connect, etc.).
Regarding the data quality: At least in Germany the ADFC maintains its own cycle path network which also contains metadata about road surface, motor traffic and such things. This is also one of the sources Google licensed for their bike stuff in Maps (although back when they introduced it they had a very hard time matching up their two or three different data sets and there were lots of errors where junctions wouldn't connect, etc.).