Mason Tvert, executive director of SAFER (Safer Alternative For Enjoyable Recreation), which ran a successful 2005 campaign to legalize possession of up to one ounce of marijuana in Denver, has long been the merry prankster of Colorado weed activists -- a prankster who knows how to have serious impact. When photos surfaced of Governor Bill Ritter's son hitting the booze at a governor's mansion party, Tvert and his posse threw a media-grabbing kegger on the mansion lawn to prove the point that the encouragement of alcohol but not pot was a total party foul. He was also responsible for arguably the most successful billboard that never actually existed: In 2005, as part of the Denver pot legalization campaign, SAFER proposed a billboard celebrating Miami Dolphins running back Ricky Williams, who'd been suspended for marijuana use. The billboard attracted national attention -- even though Tvert never actually put it up.