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1. Managing a social calendar is difficult and inefficient: You have to call/text tons of people, take into account availability, remind people to come, figure out who's bringing what, etc.
2. Most event managers (Facebook, Meetup.com, etc.) are for planning events far in advance. It's very difficult to plan something on a whim (like a basketball game, dinner, game of chess, ...)
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4. This is Adam Smith's idea, but he thinks that online dating is a completely flawed model because meeting people by friends of friends is the best way to form relationships. http://blog.adamsmith.cc/2011/02/towards-better-online-dating.html
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