This recently happened to me... there was a set of singletrack I and my friends enjoyed because of the obstacles - logs, rocks, ruts etc. Unfortunately the singletracks were also used by some young gonzo jerks who were traveling from one location to more difficult trails. One weekend they came in and removed all the logs, rocks and ruts making the trail a smooth "freeway"... those guys were lucky I wasn't around to find them doing that! The only comfort I take is that shortly after, we had some heavy rains and the whole area flooded. It's been under water for 6 months now and I suppose will be back to its normal, technical self after the water receeds.