So I'm looking through the MBP service manual (http://forums.macrumors.com/showthread.php?p=2166412&posted=1) and there are some very interesting tidbits in there. Check out the size of the heatsink in the MBP. It's basically three tiny metal contact points on a heat pipe and a couple of small radiators at the end. Apparently it's enough cooling for the North Bridge, CPU and GPU. The service manual also contains pictures, but this diagram is the easiest to see.