Why is mountain biking so addicting? It seems that once someone starts mountain biking, they feel a need to do it as often as possible – at least weekly. And they become impervious to information about the harm that mountain biking does. (That's why it is extremely unfortunate when land managers or their staff start mountain biking.) Apparently, some people have an especially strong desire or "need" for danger and thrills, and it seems to be accompanied by an unusually low concern for the welfare of wildlife, the environment, non-bikers, or anything else that gets in the way of their thrill-seeking. A phenomenon that may be related is the existence of psychopaths -- people who seem to be genetically devoid of moral feeling. See _Without Conscience: The Disturbing World of the Psychopaths Among Us_, by the brilliant scientist Dr. Robert Hare. I highly recommend his book. As far as I know, in Hare's terminology, mountain bikers are sociopaths, not psychopaths.
http://home.pacbell.net/mjvande/mtbfaq- Michael Vandeman, Ph.D.