Leo Burnett famously stressed the importance of loyalty in business -- to one another, and especially to clients. On Dec. 16, 1958, a memo on green paper titled "Scratching the Back of the Hand that Feeds You" was circulated to the agency's staff. Fifty-three years later, his principles are still valid (which is why the agency sent them out today to staff as a reminder).

We particularly like the postscript, where the legendary adman casts a spell on any staffer who dare eat Wheaties over a product made by Kellogg -- still a client to this day. "I hope he chokes on them," he wrote.