Even better, that number is already outdated - the article states that the Model S has a 5.1% market share already.
It should be noted though that the Norwegians can afford to be environmental - they make ridiculous amounts of money from their offshore oil fields. Also, they have plenty of cheap electricity from hydro.
We can "afford to be environmental" the same way any country would be able to afford to be. The real difference is our wealth distribution which is leaps and bounds ahead of most of the world, here in Norway a higher percentage of the population are simply able to afford the car and that is what we're seeing in Tesla's market share.
Edit: About $9.30 per gallon (using 14.83 nok per liter in dollars per gallon via google)
GDP per capita 2012 for Norway: $99,557. US: 49,965. (Sweden: $55,244)
The last decade has been exceptional, though part of the reason is the NOK is vastly stronger against the dollar than it used to be (then again part of the reason for that is that the Norwegian economy is as strong as it is)
(EDIT: that's World Bank numbers, btw. IMF and other sources give slightly different results, but the relative difference is pretty much the same; if you factor in purchasing power parity, the gap is substantially closer, though)
That said, Norway is very smart. They correctly perceive that GDP from oil production isn't really income, but rather simply liquidation of assets. They know they can't afford to spend that money, so they save it (effectively turning it from one kind of asset into another).
My point was that the fact that Norway produces oil doesn't trivially lead to more people buying electrical cars.