The local defense forces don't have to beat the Taliban, just hold them off long enough for forces (ground or air) can pound them, chase them off, and disperse them. Then hopefully kill them in pursuit. Afghanistan especially can't afford the cost of paying for regular forces to garrison every populated area.
This article condemns the effort in Afghanistan:
Abdul Jabar Farhad used to be just another illiterate old mujahideen commander living off past glories in Afghanistan's countryside. Now he is at the forefront of a controversial project that has become a litmus test for NATO's exit strategy.
His band of 150 men is part of the nationwide Local Police program, funded by the United States, that arms and pays village forces to defend rural areas from the Taliban.
The scheme is inevitably compared to the US-sponsored Awakening Councils in Iraq, where tribal groups were successfully mobilized against Al Qaeda. Here, however, few people are convinced it will work.
Amid growing accusations of violence and criminality, the feeling among many Afghans is that these militias are destined to run wild and cause the kind of chaos their predecessors unleashed when the Soviets left in 1989.
This is not to say that it is easy to do. There very well could be some serious problems with some or even all of the Local Police units. Supervision and leadership are needed to keep them working with the government forces rather than as freelancing gangs.
I do worry that efforts to make Afghanistan a unified state governed from the center will make local defense forces indifferent to working with the alien central government. But if local defense forces work with our special forces and provincial and tribal leaders who work with us, there is more chance that Local Police will be a force to resist the Taliban.
But the idea that it is just a mistake to follow this path is mistaken. If there are problems with the Local Police problem--fix them. If we can't get Afghans to defend their villages and neighborhoods, we'll never be able to do it for them.
And this is the "good" war against jihadis who might want to kill us, right? Work the problem.
UPDATE: Local defenses in action:
Elsewhere in the east (Ghazni province) tribal militias have massed and chased Taliban out of at least ten villages. The locals disagreed with Taliban lifestyle rules (especially shutting down schools). The Taliban risk heavy casualties (from smart bombs) if they bring in a large enough force to defeat the tribal fighters. These tribal uprisings against the Taliban are increasingly frequent. In addition to the threat of smart bombs, the Taliban are also hampered by a growing number of Afghan police and soldiers. While these can be bribed, there is not always enough cash available for this, or there are too many people to bribe and if you miss some, they will be the ones blocking a road when you are rushing reinforcements to some Taliban under attack by tribal fighters.
This brings up my point that when the Taliban choose to take on even the lower tier local defenses, the Taliban have to look over their shoulder for the regulars and air power to show up.