It's not a trivial issue.

We had one death on the Cedar River Trail summer before last due to a fast cyclist hitting an older woman who was apparently confused by his callouts. She was walking and he was overtaking her. We also have a friend who was jogging and was hit by a mountain biker going too fast out of control on the Lake Youngs Trail that same year. She survived, but was in the hospital a long time and had to have multiple surgeries for facial and shoulder reconstruction. Both accidents were very avoidable had the cyclist been riding at an appropriate speed for the situation.

I'm a road cyclist and cycle commuter, and I wish I could ride fast on the trails because they are nice and smooth with no cars, but it just isn't safe enough to be passing people at high speed. Yeah, you could argue that they create much of the risk through I-pods in their ears, dog leashes, uncontrolled kids, panicky elderlyness, and obliviousness, but everyone else on the trail can pretty safely co-exist. It's really our high relative speed that creates the problem. I accept that if I want to ride on a trail when it's not deserted I have to limit it to about 15 mph and slow way down to pass kids, older people, dogs, chatty groups of walkers, the I-pod deaf, and horses. I ride on roads if I want to go fast, or go on the trails very early.