I walk 4 miles a day on city sidewalks. The number of times I have to yield to bikers on the sidewalk is disgusting[0]. And some of these bikers are going fast. I once saved a child that was about to run out of a store. I could see, from my vantage point, the biker and the child set for a collision course. I stepped in front of the biker, doing about 20 mph on the sidewalk, to stop them. I got an earful of 4-letter words not a thank you.
Of course, there was the 20-something woman killed in a crosswalk by a biker running a light in SF a few years ago.
As a pedestrian, I have no love for many drivers or bikers, since they are a constant source of danger.
EDIT:
[0] I had an argument with a young woman at a light once, where I told her politely that she wasn't supposed to be on the sidewalk. He response? To tell me I was a selfish person not wanting to share the sidewalk.