The big tech companies are spending billions to stockpile patents. Earlier this month Microsoft paid more than $1 million each for 925 AOL patents, Microsoft then sold 650 of them to Facebook for $550 million. Google and Apple have aggressively hoarded patents, as well. The reason? Yes, these companies still create amazing new products, but the game has shifted. In Silicon Valley, companies spend their fortunes protecting market turf through the aggressive defense of the intellectual property acquired by buying up existing patents. Microsoft is worried about Google’s Android operating system, Facebook is worried about Google Plus encroaching on its social networking dominance. Apple and Google fight for dominance in smartphones. And so the companies buy more and more patents, and keep armies of lawyers employed suing each other for infringement. How would the great inventors of the past century have fared in this environment? Edison accumulated 2332 patents of his own, and was frequently involved in lawsuits over them. He might have been the richest man on earth had Microsoft and Google been around to take them off his hands a hundred years ago.