I've had scary encounters on three of the four trails I ride on. I don't know what the solution is. All of them are in populated areas, with roads very nearby (adjacent to, in sight of) the trail.

http://tinyurl.com/k94b9

This incident (only time I ever rode without a helmet- now have figured out how to get my hat under it- so you don't need to comment on that!) took place after I quit riding on another trail after I had a scary incident with a couple big teenagers (who were probably only thinking of robbery, not murder).

The creepy guy never confronted me, never harmed me or anyone that I know of, and I continue to see him at various points along this 46 mile trail, including within a couple miles of the isolated parking lot. I am still very unnerved by and very afraid of him.