Eh, depends on the location. My sister rode a bike every day for about 4 years (she didn't have a car). She always rode on the sidewalk because she rode at a slower pace, the sidewalks generally didn't have any people on them, and in her neighborhood if you tried to ride in the road you'd get mowed down by vehicles. There's really some places where it makes most sense to ride on the sidewalk even if you aren't supposed to.