The dirty little secret in the tech world is that companies knowingly violate each others patents. There is a business decision made that weighs the value of expected revenue against the possible exposure to a lawsuit if a patent claim actually takes place. If the exposure is too great, sometimes efforts are made to acquire the technology through licensing, joint-venture, merging/purchasing the patent holder, etc... also the decision might be made to spin-off the product to a subsidiary, or not develop the product at all. Most of the very public patent disputes are issues that have been in contention for years, and the headline step of filing a lawsuit is simply one company trying to force the other party back to the negotiating table where they can both agree on a price to share or transfer the patent. When the companies settle on terms (sometimes financial, sometimes not), all of a sudden the patents are no longer an issue... case in point:
http://www.microsoft.com/presspass/press/2010/apr10/04-27mshtcpr.mspx