I am an engineer at Google. No, we don't read through patents to figure out how to do something. We are not idiots. If I wanted to implement a pinch/zoom system, I would just do it. It's not rocket science. In fact, I believe I did do it, before I worked at Google. I was writing code for an iPhone app on a version of IOS that did not have the gesture recognizers available in the public API. It's not that hard to recognize two points moving away from each other.