Introduction

Abstract

The terrorist attacks on the World Trade Center and the Pentagon last September shocked us all. Many reached for the telephone to contact loved ones and watched TV or listened to the radio for news in the days directly following the attacks. Others, however, sought support and exchanged information via online communities. In fact, some 30 million Americans---about one-third of all U.S. Internet users---turned to email, mailing lists, instant messaging, chat rooms, and threaded discussion systems [1]. They wrote detailed eyewitness descriptions and tender words of comfort. They engaged in soul-searching debate about why these events occurred, what response was appropriate, and what should be done to avert future atrocities.