For those expressing concern that 'abandoning' Afghanistan will lead to a Taliban takeover, these two maps from the International Council on Security and Development paint a bleak picture.
It seems that the Taliban has already taken over almost the entire countryside.
I apologize for the low quality of these pictures- I recommend you go to the ICOS link above, and check out this more comprehensive post about the Taliban resurgence published at DailyKos.
The dark red symbolizes heavy Taliban/insurgent activity, the light red represents substantial Taliban/insurgent activity, and the gray indicates light Taliban/insurgent activity. The top map is from September of 2009, while the bottom map is from November of 2007. In those two years, NATO forces have surrendered an additional quarter of the country to either the Taliban or anarchy, including most of the border with Pakistan, such that 80% of Afghanistan is under heavy anti-NATO attack. It is not a pretty sight, rather an unfortunate reminder of how difficult any military victory would be.