Welll,,,
Yeh, mS did make this decision BUT'
why no car charger? For that matter there are a number of compact 12v sources that could charge the surface if MS made a car cable available.
I agree and can only assume a car charger is coming. This does seem to be an oversight rather than a design decision. You can always use an inverter in the car but generally they are expensive, large and noisy, which makes them far from the best solution. For cars, a 12V charger at 2A would give the necessary power however more info is necessary (see EDIT below) since the standard for electronics seems to be 5V which would need 4.8A of current to charge the Surface, or more than double a standard high power USB charger.
Other than listing the output as 24W there isn't much else in the way of specs on the charger. However, doing some quick calculations (thanks Google) here is a quick comparison of other chargers.
EDIT: I finally checked the fine print on the charger and got the Surface charger power specs below.
Surface RT 12V @ 2A = 24W of charging power.
Standard USB 5V @ .5A = 2.5W of charging power.
Standard USB 5V @ 1A = 5W of charging power (these are what most USB ports output).
High power USB 5V @ ~2A = 10W of charging power (specialty bricks included with newer Android and iOS tablets are ~2A).