In his first small store, Sam Steinberg says, customers were like family – they'd pitch in to help at busy times. No more. This fifth part of the Corporation series, filmed in stores, at consumer meetings, and in corporate plants and offices, looks at how the corporation that grew from that first small store attempts to hold its own in the three-way tug-of-war with suppliers, competitors and consumers. One strategy in the struggle over price and profit is for the corporation to capture the supplier's share of profit by producing its own brands of foodstuffs and merchandise; another is to …