Originally Posted by bacon12
You underestimate the money that MS would throw at them, valve has shown with l4d that they are committed to supporting the 360.
They support the 360 because they like making their games available to as many people as possible. That is why Source has low spec requirements, and why Steam makes it easy to join an online game. Valve is all about including people, and Natal would alienate like 90% of their audience.