Riding on the sidewalk is extremely dangerous. Drivers will often turn (without signalling even) and not notice a bicycle coming up from behind them on a sidewalk. Driver also often back out of driveways without being able to see a bike approaching on a sidewalk.
Cyclists should be taught how to ride safely on the road and use all of the proper safety equipment.
I've commuted by bike for years and frequently shake my head when I see the behavior of other cyclists.