Apple American Group has done just fine by focusing on one concept, Applebee's. It's done so well that it could well be the largest restaurant franchise in the country. So why is Greg Flynn now getting into Taco Bell? "It's simple math," said Flynn, CEO of the San Francisco-based Apple American Group. "If you add 10 units from a base of 10, that's good growth. If you add 10 from a basis of 480, it's not." The upshot: if Flynn's company was to maintain a strong growth rate, it needed to get into something else. So two years ago, the company started taking a comprehensive look at the restaurant industry and ultimately concluded that Taco Bell was a good bet, thanks largely to its lack of direct competition in the ultracompetitive restaurant market.