Yes, Google is trying to ward off being picked to death by a myriad of utterly worthless (in the market, not legal sense) patents. Yes, Google is likely in violation of several thousand patents with Android, and all of its other software products. Guess what? So is damn near every other developer on the face of the planet, but Google has a big fat target painted on their back because of Android's success. They would be crazy to not try to acquire a defensive patent portfolio.
I'll guarantee you that I violated a good half-dozen patents in the course of my absolutely routine work today. That doesn't mean that I'm a mean nasty violator out to undermine free enterprise, it means that software patents suck. Apple and Microsoft have both proven that they will use these garbage patents offensively to drive competitors out of the market, and Google is left in the position of "acquire means of mutually assured destruction to protect ourselves with or die by horribly broken patent law". Which do you think is the sane and responsible course of action?