The year 2008 may have been a bad one for most Americans, with layoffs and foreclosures and bank failures rippling through the economy, but for Exxon Mobil, the world’s largest publicly traded oil company, there was reason for joy. Exxon posted an annual profit of $45.2 billion, the largest profit ever achieved by any American corporation. The oil giant responded to the awkwardness of announcing this bonanza at a time when the country is facing deep economic problems by emphasizing that its fourth quarter profit was down sharply…to a mere $7.8 billion. Rival Chevron didn’t do badly either, with earnings of $24 billion for 2008.