Apart from stretches of Germany's autobahn with no speed limit, there are few public motorways in the world where drivers can use more than a fraction of the power turned out by the world's 10 fastest mega-cars. That has scarcely dented demand among deep-pocketed enthusiasts for these near mythical beasts which cost as much to buy as several homes. Most are quickly sold out. Fuel consumption is not something that concerns buyers of these gas-guzzlers. But as a sign of our changing times, electri