So Musk himself decribed it as a "cross between a Concorde and a railgun and an air hockey table". So why do people keep talking about tubes ?

Wouldn't a Ground Effect Vehicule (http://en.wikipedia.org/wiki/Ground_effect_vehicle) fit the descripton better ?

Edit : thought a self powered super-sonic GEV would be hard to pull of.

one of the more appropriate links...https://en.wikipedia.org/wiki/A%C3%A9rotrain