During the past year or two, federal trustbusters have gone after some of the biggest names in U.S. business. Antimonopoly suits are now in various stages of litigation against several giants, including AT&T, IBM, Firestone, Xerox and the big three in the rental-car field: Hertz, Avis and National. Last week the Justice Department turned its attention to some of the biggest banks and insurance companies, charging that they too are in violation of U.S. antitrust laws.
At issue are interlocking directorates—arrangements under which a director of one company serves simultaneously on the...