Should we support hoarding?

Yahoo is suing Facebook for violating some of its patents for technologies it both uses and doesn't use. Yahoo waited years to take this action and it wasn't until Facebook announced its IPO that they went "live" with their lawsuit. That seems predatory on the surface but I don't know enough to make a judgement that means anything. Here's what I do know: companies that file for patent protection on technologies they don't use or license for use to others shouldn't be allowed to hoard those assets for the full 20 year life of a patent. Why? Because it stymies progress, isn't in the best interest of a free marketplace and doesn't honor the original purpose of patent law: protection for inventors in the marketplace. If your invention never reaches the market, then what are we protecting it for? PS Audio is in the process of patenting a new sound delivery system that we believe will change high-end audio forever once released. Does it make sense for us to patent it and then sit on it for 20 years so no one else can build it? I don't think so. I think it makes sense to set reasonable limits on such things. Either I can turn it into something over a reasonable period of time or I should give it to the world. Hey, maybe I'll patent this idea of putting limits on patents.