Through more than 40 years of U.S.-Soviet confrontation, the Central Intelligence Agency warned American presidents that the cold war might turn hot. But World War III never happened, and now the agency is being criticized for failing to foresee the speed with which communism would collapse in Eastern Europe. This and other recent intelligence breakdowns have given the CIA's critics more reasons to question the agency's effectiveness. But while some observers see the agency's days as numbered, others say the CIA is needed more than ever to confront the growing threats of nuclear proliferation, narcotics trafficking and terrorism. And some believe the CIA could help halt the erosion of America's competitive edge by ferreting out foreign business secrets for U.S. companies.