You can be very much obsessed even in building something within Google. Obsession and passion are not measured in money.
By your logic the creators of Unix weren't obsessed with it, because "what did they have to gain (from AT&T)? Just a promotion".
I'd say being passionate in the specific thing we're discussing (Facebook vs Orkut) doesn't mean a thing. What exactly that more advanced Mark HAD to show for his passion? Yes, he has the far far better business now, but where was the passion factor at play in making a better offering THEN?
What I see is business opportunities and mistakes in Orkut vs Facebook.
Not any engineering (or other) passion that resulted in a visibly better product.