1) The "enemy" in Afghanistan is totally independent and organic. This may seem like common, mainstream knowledge but he took it to an extreme level or granularity. According to Hoh, troops will enter a peaceful, non-combat zone, like a new valley in the mountains. There may be no good reason to even go to the valley from a strategic sense. Its just another piece of land that someone decided we should "hold". And all of a sudden locals spring up to fight American forces simple because they are on their local tribal land and the Taliban or some related group may decide to pay locals to support this. So in this scenario of local tribal militias at every turn, there's basically no way for a small, though highly sophisticated, occupying force to "win". There's no central command to surrender or to kill. And there's no effective, domestic central government to enter and take control if we do clear a region of active insurgents temporarily. We can't win in this environment.
2) The second and really more important factor is our very purpose in fighting this war has evaporated. We went to kill, capture and disrupt Al Qaeda operatives and their camps. We did that and Al Qaeda's people have dispersed or been killed. Ho argues that we don't have to worry about them returning to create new training camps for 2 reasons. First they have many countries to operate in, so spending billions of dollars and hundreds of lives in afghanistan is a waste. Secondly, AL Qaeda has evolved to a completely dispersed organization with small cells of a few people communicating and coordinating over the internet. They've learned this is the only way to survive now and they won't go back to big training camps with large groups of people. We are once again fighting the last war while our enemies have moved on to new tactics on a new battlefield.
In general this analysis fits in with what other sources I find valuable have said and with historical analogs of the situation. So now Obama has to have the courage to be the one who "loses" the war that Bush started and the top general in charge still says he can win. And he has to do this while the country is in a vast recession with record unemployment levels. That a tough job for anyone and I sympathize with him. But in the end I think he has to end the war and accept the political repercussions.