U.S. Marijuana Enthusiasts Gather For Mass Pot-Smoking Celebration

BOULDER, CO - APRIL 20: A student smokes a marijuana cigarette during a "smoke out" with thousands of others April 20, 2010 at the University of Colorado in Boulder, Colorado. April 20th has become a de facto holiday for marijuana advocates, with large gatherings and "smoke outs" in many parts of the United States. Colorado, one of 14 states to allow use of medical marijuana, has experienced an explosion in marijuana dispensaries, trade shows and related businesses in the last year as marijuana use becomes more mainstream here. (Photo by Chris Hondros/Getty Images)