At a tangent, but relevant: Lets not forget what the regional stakes are. Being the "biggest tribe" is not just about Afghanistan. In fact, I would submit its not even primarily about Afghanistan. Why is the US IN Afghanistan? Why should the US care who rules Afghanistan and who is the biggest tribe there? I think NOW THAT ITS THERE, one of the big reasons to stay and win is because it shows regional powers who is the biggest tribe. And IF one buys into the whole superpower deal, then that is much more important than showing some small villages who the biggest tribe is. You can see this dynamic in action in Pakistan right now. The Pakistani army has looked at Obama's good hearted wavering on Afghanistan and reached the (probably correct) conclusion that this particular American tribe is outa here in the not too distant future. Hence the reluctance to accept Kerry-Lugar conditionalities about the role of the army in Pakistan AND about Pakistani efforts to use jihadi proxies against India. On both these counts, GHQ now seems to think they can get America to blink (again, I think they may be right; the first has not historically been an American priority, always loved military dictators in third world countries, and the second is India's headache, not America's). The sticking point right now is the "good taliban" (just my guess, I have no inside info) and GHQ may be calculating that if they hold out long enough, Obama will accept the good taliban at least in Eastern-Southern Afghanistan and a few years later the good taliban can take care of the rest of the country, by which time American troops will be gone and no one will care.
Personally, I am not sure this is a correct assessment and even if it is, the net result is going to be a huge disaster for the region (where an American victory would be painful for some egos, but a net positive for the long suffering people of the region). But the american tribe is fast losing credibility and that means that eventually the coming civil war will be fought between India, Pakistan, Iran, Russia and China and their proxies. Thats bad for the region, but if I was an American officer, my main concern would be "If we are not going to win this tribal war and act all superpowerish, then we shouldnt be sacrificing men just to make it look good for a few years". Go in, or get out.