Following up on my last post here is the view from Pamela Samuelson:Why software startups decide to patent ... or not
Two-thirds of the approximately 700 software entrepreneurs who participated in the 2008 Berkeley Patent Survey report that they neither have nor are seeking patents for innovations embodied in their products and services. These entrepreneurs rate patents as the least important mechanism among seven options for attaining competitive advantage in the marketplace. Even software startups that hold patents regard them as providing only a slight incentive to invest in innovation.
She also lists a variety of reasons why these software entrepreneurs decided to forgo patenting their last invention. It's a very interesting write up.