People weren't getting their jobs through their friends. They were getting them through their acquaintances. Why is this? Granovetter argues that it is because when it comes to finding out about new jobs -- or, for that matter, new information, or new ideas -- "weak ties" are always more important than strong ties. Your friends, after all, occupy the same world that you do. They might work with you, or live near you, and go to the same same churches, schools, or parties. How much, then, would they know that you wouldn't know? Your acquaintances, on the other hand, by definition occupy a very different world than you. They are much more likely to know something that you don't. To capture this apparent paradox, Granovetter coined a marvelous phrase: the strength of weak ties. Acquaintances, in short, represent a source of social power, and the more acquaintances you have the more powerful you are.
Source: The Tipping Point: How Little Things Can Make a Big Difference, Pages: 54
Contributed by: ~C4Chaos