Obviously the horse can still do things that the gas car can never do, and the gas car will always be able to do things the electric car can't do. But they have really different uses and advantages.

I'm sure the gasoline companies would love to keep their 100 percent monopoly on transportation fuel.

There are not a ton of people buying cars - cars are expensive. So people usually go for the cheapest car they can get. And if the price of gasoline falls again, it makes the savings that you get with an electric car harder to realize.

Resistance to change is always the biggest obstacle.

In the case of all the carmakers, there's a certain amount of greenwash. Take Toyota: They were pushing the Prius while they were meanwhile marketing the hell out of the Sequoia and other models with terrible gas mileage.

Solar, for example - which has typically been thought of as so expensive - is cheap when compared with, for example, the cost of cleaning up the Fukushima nuclear disaster and the Gulf.

I like to take folks back to the turn of the century when people said 'gas cars can never replace horses because you can feed horses at your house, you get along with them, they're nice.'