For those who have not entered the world of Twitter, it is hard to fathom why people feel compelled to stream their lives to strangers 140 characters at a time. And such non-Twitter folk are also unlikely to fathom the purpose of blogging, especially in a world with more than 170 million blogs. Imagine the non-tweeting non-blogger’s disbelief, then, when they read story after story about how Twitter, Facebook, Wordpress, Posterous and the other “Social Web 2.0” heavyweights are changing the world as we know it.