What Were They Thinking?By: Robert McMath Those ignorant of the mistakes of the past are bound to lose a lot of money. That's why Bob McMath founded the New Products Showcase and Learning Center a "Smithsonian for Stinkers," Business Week dubbed it. There, executives from top corporations pay huge amounts of money to rummage through some 80,000 products gone awry. Their mission: to avoid the misguided, expensive, and occasionally ludicrous mistakes that trip up even top