Business history is littered with ideas that looked great on paper but were awful in operation. A colorless Pepsi and Diet Pepsi sounded like a great idea until you drank Crystal Pepsi and Diet Crystal Pepsi with that weird fruity flavor. A Keurig soft drink machine with Coca-Cola seemed like a home run until you saw the huge machine that produced 8-ounce drinks, that was more expensive than a 12 ounce can of the same drink. With 401(k) plans, there are some ideas that look great on paper but are just a potential nightmare for you as a 401(k) plan sponsor.