I see this happen all the time and have no idea if it's legal or not...
My city has spacious bike lanes on almost all the major streets and serious cyclists are always using them... but people are riding fast on the sidewalks all the time in my neighborhood, and it's starting to get to me.
Yesterday morning, I was out running pre-dawn on a sidewalk that was barely 3 feet wide. Coming around a blind corner, some 20-something on a mtb, wearing all the latest iPod gear came roaring around the corner (going the wrong way, I might add) and nearly plowed right into me. I barely had time to jump out of the way, but the end of his handlebar grazed my rib cage and sent me into a bush which was far too prickly for my liking. I heard the yahoo say, "Whoa, sorry" but he never stopped or looked back as he rode away (no lights either, BTW). I was so mad I started yelling at his backside, but I doubt he heard me over the earphones. I was wearing my iPod, too, but it wasn't very loud. How apropo that the next song was "American Idiot" by Green Day.
I figured, well, at least he won't do that again. Nope. I went for a ride this morning and saw the same guy doing the same thing! I felt like chasing him down and giving him a piece of my mind, but in a dark place with no witnesses around, I didn't think I should.
I tried to look up the city laws regarding cycling but couldn't find any references to bikes on a sidewalk. I had never been hit like that before, but I would say I run across a biker on a sidewalk (who forces to get out of the way) an average of once every three runs. Usually on BMX bikes, ocassionally mtbs. All I can do it yell and point out the bike lanes. Ooooh, that makes me mad. <Fists all balled up>
Thanks for letting me vent.