One of the most painful was McDonald's (NYSE: MCD), which Berkshire Hathaway (NYSE: BRKB) (NYSE: BRKA) sold in the late 1990s in a move Buffett flatly called "a very big mistake." I think Greg Abel, Berkshire's new chief executive officer, will eventually buy it back, and the reason is simple: McDonald's is a textbook Berkshire business. The result is capital-light, remarkably predictable cash flow, exactly the quality Buffett spent his career hunting for. A wide moat, durable earnings, dependable and growing cash returns: This is the archetype of the kind of company Berkshire was built to own. It is a company Berkshire knows well and already wishes it still owned.