found this article...while it's from jan. 2008 it proves that assholes are everywhere so be alert on the trails!

FULLERTON, California — Police said they arrested a man who acknowledged digging holes on a park bicycle trail in southern California as payback for nearly being run down by a cyclist.

Warren John Wilson, 52, faces a single felony count of vandalism, police Sgt. Linda King said Friday.

King said nearly 50 holes measuring about 1 foot by 2 feet (30 centimeters by 60 centimeters) have been found since June along a trail at Laguna Lake Park, and in some cases attempts had been made to hide them from cyclists. She said some riders went over their handlebars after hitting the holes, but none reported major injuries.

Detectives watching the trails questioned Wilson, who said he had nearly been run over by a mountain bike rider and began digging the holes in retaliation, King said.

Police said Wilson had been released from custody. A phone listing for him could not be found.