Ultimately you have to deal with people beyond just shooting them every time they pop up. England had to do it with the IRA, chances are NATO will have to enter into discussion with the Taliban.
As far as Karzai goes... I have to ask: What is the alternative? So far as I can see there is no one else willing to step up.
But ultimately Afghanistan is a colossal screw-up on just about every level. I don't think anything anyone can do at this point will fix the issues we have left to fester for so long (which we could have dealt with if only we had not bothered with Iraq).
No matter what Obama does at this point, he's going to be wrong and that is wholly and solely down to decisions made by Bush.
Also, welcome to CH, enjoy your stay 
Agreed. I can't believe nobody decided to google 'Northern Ireland Troubles' before invading Iraq. At the height of the troubles here, there were 35000 British troops on the streets. All it did was antagonise the protagonists, and make life hell for the civilian population as a whole.
40 years later we have peace on the streets, because people sat round a table and are trying to sort things out.
How did anyone think they could invade a country the size of Iraq with limited resources, and sort it out in a few months?
Stupid bastards.