I guess I still feel it has more to do with marketing strategies than with basic economics - although these are critical as well.
Having lived through unpleasant experiences with a sole customer - the USA - for other Canadian products, I don't like the vulnerability that this type of buyer/seller relationship. I refer to the soft wood lumber dispute, the recent beef embargo placed against Canadian beef, rumblings against heavy Canadian oil with musings about a discounted price, as well as the gap between WTI and Brent priceing.
It just makes sense to me to be able to sell to more than one customer, which is what the Northern Gateway would open up.
To our American friends, I am not some sort of blue-eyed sheik; in fact I just spent a week in New Orleans, checking out Frenchman Street.
The US will pursue its own interests - as should Canada.