Generation X or HIV? A recent Wall Street Journal/NBC News survey on the defining events of American lives shed light on this bloody century. Seniors claimed World War II, while boomers cited Vietnam. Over half of those 18 to 24 named a different war -- the AIDS epidemic, which overshadowed the Reagan presidency and the end of the Cold War. Said survey honcho Peter Hart, “This generation labels itself not with a collective experience, but a collective fear.”