Out in my area we have a rather lengthy bike/walking trail. It's rather nice, one of my coworkers actually rides it a few times a week. However, not long back there were a few individuals "living" along the trail. If you were out alone, or even as a group but without sufficient protection, you were fair game.
At one point, one such individual had broken into an old woman's house who lived along this trail and was actually living in her basement (without her knowledge, of course) coming up into the house when she slept for food and to raid her liquor cabinet. The one night she couldn't sleep, she caught him in the act and he darn near beat her to death. When the cops were called, they found his "apartment" complete with all the things he had taken from the upper house, including her shotgun. He was apprehended by armed citizens - link to Buckeye Firearms digest
. Link to local paper article
I trail off, but it doesn't take much to, in the case of a cyclist, hide by the side of a trail and toss a stick between the spokes. But that's a bit nuts that drivers actually harass you to that extent - I've gotten a little upset when I couldn't pass one and was stuck at 15 MPH for a few miles, but never even considered harming them.