You can't "sit on" patents. The whole point of the patent system is to get an idea out there so people can use it. As a patent holder you're required to licen

You can't "sit on" patents. The whole point of the patent system is to get an idea out there so people can use it. As a patent holder you're required to license your invention for a reasonable amount (I'm not really sure how that's determined - probably in court). If you don't, a judge can put your invention in the public domain and give you nothing. The stories you hear about the 300 mpg carburetor and machines that produce power from the spin of electrons? These devices, if they actually existed, would have to be bought and hidden away without ever entering the patent system. And the buyer (oil companies, is it?) would have to take the chance somebody else would patent the invention for which he paid millions.