"Traditionally, patents were only granted on tangible things, such as physical devices and chemical processes. But a series of court rulings in the 1980s opened the door to patents on more abstract processes, such as business plans and software code. They also lowered the standards used to approve patents, says Mr. Ravicher. What followed were a flood of patents, covering everything from the idea of buying products online with a single mouse click (Amazon owns that one) to the aforementioned tree-swing patent. As long as large corporations held the patents, things remained fairly peaceful. There has always been a kind of uneasy “mutually assured destruction” standoff among giants such as IBM and Microsoft, each holding patents that could be used against the other."