This is true, however for these large companies many of the patents are filed as a defensive measure. Its fairly uncommon to hear them sue someone for patent in

This is true, however for these large companies many of the patents are filed as a defensive measure. Its fairly uncommon to hear them sue someone for patent infringement, and they probably have a patent on just about anything (MS has a patent on the strlen algorithm for example, its really insane). In other words, worry about getting sued by a patent troll not a big company. Also, perversely, I think you better off not even looking for patents in the first place because one of the factors that can go against you in a patent lawsuit is whether or not you were aware of the patent in the first place.