In 1987, Lou Pritchett, the vice president of sales at Procter & Gamble, had a radical idea. He phoned Sam Walton and invited the visionary chairman of Wal-Mart on a two-day canoe trip. There on the South Fork River in Arkansas, Lou made Sam and offer no profit-minded person could refuse: the chance to forge a partnership between the two colossal firms. This now legendary trip marks the culmination of a lifetime devoted to building customer relationships. Sam wrote Lou, "Thank you for what you have personally done to bring our two companies together and develop a relationship that I think...