That's absolutely true, it's far too easy to get in a situation like that even without considering patent law. I just think patents make the scatter-gun approach too accesible, and the damages are far too high. Software doesn't need to protect R&D costs on FDA studies and years of testing. If the goal is to foster innovation, either software patents should be abolished, or there should be very reasonable limits to damages, or there should be a simple and inexpensive way to trigger a review that invalidates ridiculously obvious patents such as "scan-to-email" and friends.