Four months ago, the baggy-jeans-and-snowboard crowd was cavorting in deep powder at this California ski resort, called Northstar-at-Tahoe. Many of the same folks are back on these 8,000-ft. peaks, today--hiking up the rough slopes, now covered with rocks, weeds and pinecones--to play a round of "extreme golf."
Mike Leslie, 30, clad in Hawaiian shirt and emerald wraparound shades, hums a Metallica tune as he climbs to a makeshift tee and swings his 3-iron. His ball sails across a steep slope before settling into a patch of daisies. "When I look at these mountains," he says, "I think of only one thing:...