Thanks for the input everyone. After reading all of the responses (and considering some parallel items from the Attacked... thread), I think there are a few things we can conclude:
1. There is no public place where a runner is immune from being hassled.
2. Women runners have a separate set of issues to deal with from men. (Note the number of male runners who actually APPRECIATED cat calls from women.)
If we throw out encounters with drunk and/or crazy people, as well as honest accidents, I see the following:
3. Hassles seem to be directed at runners when the runner is seen as some form of threat (generally, an imagined threat).
I say this because the hasslers are usually part of a socially or economically powerless group, and thus, have an exaggerated need to express dominance.
I think this explains the two largest groups that are implicated over and over, namely high school kids and so-called "rednecks". This would also explain the instances of middle class drivers who apparently see runners as a reminder of their own losing "battle of the bulge" (there was one instance I specifically remember where the driver adimtted as much). Consequently, older runners are probably not seen to be as threatening as younger runners, perhaps because the general public recognizes that a 40-something running on the road alone is "just a jogger", but a group of running teens might "spell trouble" (pure conjecture).
In general, it seems that areas in the Northeast and Canada have fewer problems than the South, while the West coast is a mixed bag. City running is not usually good, but backroads are not good either if they are populated by the afore-mentioned "rednecks". Municipal trail systems generally seem OK, and it is smarter to run on sidewalks when available than in the streets. And of course, stay away from groups of teens, particularly if they are hanging out and acting cool (with or without cars). I must admit though that I often run by some HS students with no problem in the early morning while they're waiting for the school bus. This could be because it's too early for them, they're a stone's throw from Mom & Dad's, or maybe they're just good kids. ;-)
Maybe we need to start another thread on "Perp Profile" to see if the above pans out with further scrutiny.