I haven't heard of any of these victims. Any links to any news stories? My guess is that it would depend on a number of factors, including the time of the day, whether the victim was walking or cycling, lighting conditions, etc.
I jump on the interurban in kent and ride it up to tukwila very early in the morning. While it is pitch black in on the trail, I've noticed people walking on it with their dogs, jogging alone, stealth biking, etc. I think I'm the only one I've seen that actually has a light. So far the only scares I've had have been trying to dodge the damn rabbits, going face to face with a skunk, and having a dingo-looking dog (who was hunting rabbits) take a lunge at me.
I would suspect the rate of crime on the trail isn't much different than any other area of town, but I could be wrong.
I usually jump off the trail around 405 for a couple of reasons. First, I prefer the straight shot of tukwila drive to the meandering trail that follows the river (when I'm going into work). Second, the lighting sucks when the trail (now called the green river trail) starts to follow the river.