In 1997, the FTC (Federal Trade Commission) found that Toys 'R' Us were guilty of illegally exerting pressure on manufacturers not to supply their toys to other, smaller retailers. As they are the largest toy retailer in the world, the manufactureres duly complied, vastly reducing comsumer choice. Just one of the many problems caused by allowing such huge companies to exist and make themselves larger by eating other, smaller, companies.
See also Wal-Mart.

viper281: Comet (British chain of electronics retailers) was always my mecca as a kid. Loads of games consoles, which my parents wouldn't buy for me (thank god). Many a happy afternoon was spent there. Sigh, those were the days :-).