Where do you live? I'm in Manhattan, and people rarely cycle on the sidewalk here. There's simply no room to do so, as there's so many pedestrians. You end up going more slowly than if you stayed on the street where you belong in nearly all circumstances.

Don't be too mad at the cyclists, though. Usually they're doing it because the city isn't providing the proper level of bike infrastructure. With more high quality bike lanes that people feel safe using, you'll see a lot fewer cyclists on sidewalks. It works in Manhattan.