The shares of Altria Group, the leading cigarette maker in the U.S., rose 20% in 2011’s flat market, and it’s up 50% over the past two years, nearly four times the market’s gain, reports Barron’s this week. Two weeks ago, the stock of Altria, the parent of Philip Morris USA, hit a 52-week high. But, warns Barron’s, investors have largely ignored the risks accompanying the domestic tobacco business. U.S. cigarette sales are in a severe long-term decline. Shipments are down by a third over the past 10 years. In 2011 alone, cigarette volumes fell an estimated 3.8%, reflecting the weak economy and an ever-growing public backlash against smoking. “Operating conditions in the U.S. cigarette industry are more difficult than generally recognized,” says David Adelman, long-time tobacco analyst at Morgan Stanley. He isn’t recommending any of the stocks.