NYT: ....high-profile attacks have been seen as a shift in Taliban strategy as they struggle against a surge in American troops that has loosened the militants’ grip on the Taliban heartland in the South and compromised the ability to stage more conventional attacks on NATO forces. American officials see the latest assaults as the Taliban’s attempt to shake confidence in the Afghan government...

General Petraeus Jan., 2011: As President Karzai made clear, the Kabul security bubble needs to be extended into neighboring provinces.” Petraeus wrote today.

General Petraeus in March, 2011 (ret. in August, 2011 to head CIA): "...it is ISAF's assessment that the momentum achieved by the Taliban in Afghanistan since 2005 has been arrested in much of the country..." Petraeus said in his first congressional appearance since he took command last summer. "However, while the security progress achieved over the past year is significant, it is also fragile and reversible."  

The latest Taliban 'attack on confidence' today killed at least 13 Americans in 'the world's toughest bus' in front of the American University in Kabul. If an armored bus in the heart of Kabul cannot be secured, it would appear that 'progress achieved' is not 'significant, fragile or reversible', but more likely fictitious or imaginary.