In the news today are the shootings at Fort Hood by Army Major Nidal Malik Hasan. Hasan had recently been assigned for deployment to Afghanistan, and had evidently tried to get out of the army to avoid that because of his sympathies with fellow muslims in Afghanistan. Given those facts, it's quite possible this was a deliberate act of terrorism, and not just the result of psychological stress.
Perhaps relevant is the fact that Nasir al-Wahayshi, head of the arabian peninsula branch of Al Qaeda, last week called for jihadists to perform simple attacks against what they consider to be enemies, using readily available weapons. Al Qaeda issues similar calls a couple times a year, and while this one appears to have been directed primarily to potential terrorists in arabia, it was issued online and Hasan might have known about it.
On the one hand, the fact that Al Qaeda has to resort to calls to random sympathizers illustrates how their direct organization has been limited in recent years. On the other hand, attacks like this point out one of the downsides to the U.S. effort in Afghanistan; while our effort in Iraq was aligned with the interests of the local population, that in Afghanistan has primary goals directed towards exclusively U.S. interests.
This particular incident also suggests we might benefit from a mechanism to allow officers to buy their way out of obligations incurred from schooling - probably the only reason why a Major couldn't just resign. Certainly it reinforces the wisdom of an all volunteer force; conscription would undoubtedly result in far more incidents like this one.
 See Stratfor counterterrorism report from 4 November 2009, www.stratfor.com
I don't think that's one of the primary U.S. goals in Afghanistan, which I believe are (1) retribution against Osama bin Laden and (2) preventing growing of opium poppies.
While the Karzai government is more tolerant towards women who don't wear veils than is the Taliban, I don't think that's the main reason why we support them; the Taliban's protection of bin Laden is in my opinion the major factor.