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For the Web's overcurious types, Twitter keeps giving and giving. Sure, Facebook and LiveJournal give professional stalkers a window into their prey's mind and soul, but Twitter is a far more valuable tool — you receive constant updates on their whereabouts and moods without the long-winded diatribes and tedious application invites. Now Twitter is rolling out a handy tracking service that will help you procure new victims. Now you can simply call up your trusty mobile sidekick, anonymously text, say, "TRACK Arrington", and every little mention of the man will be Twittered your way. If one of your target's pals — perhaps JasonCalacanis? — has a particularly juicy tidbit, send a "WHOIS" Twitter, and you can start stalking his friends, too. With the username and identity in hand, you can easily "follow" him on Twitter, or "coincidentally" appear in the same cafe, and pitch the man on your startup with a healthy plying of coffee and pastries. (Photo by Wanda Gould)