[HighLordDave]

If you are an oil company or company that makes money off of fossil fuel products, say ExxonMobil, Ford Motor Company or BP, and you own the patent on a clean-burning fuel engine, why would you release a product to compete with your existing line of products, which are making you lots of money?

For instance, in the 70s, Exxon and Shell Oil bought up a bunch of patents on low/zero-emmissions internal combustion engines and electric fuel cell technology and put it on a shelf somewhere. If this technology had been pursued, we wouldn't need the oil from the middle east (or ExxonMobil) to run our cars. Why would you want to introduce a technology that makes your current line of products obsolete? In the long run, it's probably a better bet to develop fuel cells, but in the short term, there's a lot more money to be made in gasoline than there is in R&D into electric cars.