For years, out-of-state moguls have flocked to this Rocky Mountain playground. Forest Mars, Jr., the former CEO of Mars Inc. and heir to the chocolate-bar fortune, owns a ranch on 82,000 acres in the southeastern part of Montana, along the Tongue River. Recently, though, there has been trouble in Mars' paradise-in January, a gas company with a "mineral lease" began drilling for coal-bed methane beneath the billionaire's property.
