Patents are offensive only. Even if you have a patent over your product, you can still infringe another patent. The reason big companies want patents "as defen

Patents are offensive only. Even if you have a patent over your product, you can still infringe another patent. The reason big companies want patents "as defense" is because they can use those patents against a competitor if the competitor sues. A good example is Apple v. Samsung. They both asserted many patents against each other. Patent trolls, however, don't infringe any patents. You can't hit them back.