Twitter and Ambient Intimacy

How Evan Williams helped create the new social medium of microblogging.

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Users of Twitter, a new social-networking tool, use the Web, mobile phones, and instant-messaging software to send and receive short, 140-character messages that answer the prompt, "What are you doing?" Launched in March, Twitter already has 500,000 users. Twitter encourages a new kind of social behavior that experts are calling presence--a shorthand for the idea that by using such tools, we can enjoy an intimate, "always on" virtual presence with our colleagues and friends.