I don't think there's inherently any problem with letting cyclists use the sidewalk. I certainly used to back when I had a bike, and I lived in a *tiny* town.

The actual problem is that road development gives way too much priority to motorists. If sidewalks were expanded more often than roads, we would see all of these problems gradually disappear. Pedestrians wouldn't be so paranoid of everything or accidentilly get clipped by cyclists (extra space, yo) and nobody would be murdered by lunatics speeding in 2-ton hunks of metal.

But then again, going by the current track record, local governments seem perfectly content with letting huge semis plow through every single not-filthy-rich neighborhood because hey, "it doesn't affect meeeeeee."