This industry leader's dividend is hard to resist, but its business is facing some serious challenges.Among ultra-high-yield dividend stocks of long standing, you don't get much more reliable than Altria Group (MO 0.77%). The company has consistently paid a generous dividend, and its stock is one of the market's rare Dividend Kings, meaning its management has enacted dividend raises at least once annually for at least 50 years in a row.Sure enough, like clockwork, Altria made its habitual once-per-year divi ...