My wife can’t seem to walk for a half-hour around Ottawa, a city with nearly a million people, without running into at least three of her friends. Some people, like my wife, seem to have a zillion of them, while others appear to be content with just a handful. Having more friends seems like a good thing: It’s been shown to make you happier, and your social circle is more important than diet, and even exercise, to your longevity and happiness.