What's the best way to prevent getting your house robbed? Put out a sign on your front yard saying "I will be on vacation starting July 2011". How will this prevent your house being robbed (at least up until July 2011)? Why rob a house when it is occupied when you can wait until it is empty.
Our President just put that sign out in Afghanistan's front yard. Who cares if there is 30k more troops... it may as well be 80k or 1k, it wont make a difference. The enemy, now knowing what we'll be doing, will make the proper adjustments in their strategy. They will hunker down and melt into the countryside, while they recruit and train and prepare for their offensive starting August 2011.
Meanwhile, Obama claims victory because no troops are being killed fighting the enemy because we cant find the enemy. Our troops all come home with much fanfare. In Afghanistan, the Taliban re-asserts itself because we have really accomplished anything. Of course, our press as well as Obama ignores this.
Its no wonder our allies don't like this strategy