In the case of President Obama, this represents a less costly and less dangerous alternative to the Bush Doctrine of perpetual war. But what happens when the Bush wars are over — as they probably will be soon — and we still have both the culture and the instruments to disabuse ourselves of anyone or anything that disagrees with us, or perhaps simply annoys us?
Important question, but resting upon dangerous assumptions. First, the Shadow Wars are probably better understood as a refinement of the Bush Doctrine, in the sense that their architects design them to preventatively take down terrorist organizations worldwide, but without all Bush's stuff about state sponsorship or the implications about invading other countries, downplaying the softer side of American power, and so forth. Donald Rumsfeld wanted Special Operations Command to run the war on terror, for instance. Obama has made a global, endless war less conspicuous -- not less global or less endless.
It's true that declining to garrison forces in Iraq (though consider me skeptical -- not outright doubtful, but I'll believe it when I see it -- on that one ) is cheaper than garrisoning them there. Same goes for drawing down in Afghanistan. It's also, at the risk of banality, still expensive to run a streamlined global war. But notice: we're talking about the upfront costs.
It's gauche these days to worry about the future blowback from the Shadow Wars, either in blood or treasure, because in the long afterglow of the bin Laden raid, they look pretty great. If, however, they result in the destabilization of nuclear Pakistan, they'll look like an epic folly and self-delusion. Faizal Shahzad didn't just say the drones were why he tried to bomb Times Square, as is constantly misreported, he cited the invasions of Iraq and Afghanistan, too. To the radicalized -- admittedly not the most logical interlocutors, but the crucial demographic here, because at one point they weren't radicalized -- there's hardly a distinction to be drawn between the Bush Doctrine and the Shadow Wars. And perhaps if the next Shahzad succeeds, as everyone agrees is likely, the Shadow Wars won't seem so cheap.
On the other hand, it's unlikely that the next Shahzad will kill remotely the numbers of people that al-Qaida killed on 9/11, so that's a point in defense of the strategy.
But the crucial point is that no American leader has articulated an endgame for this amorphous global war, let alone explained how the actions s/he takes gets us there. Obama has lowered a 767 from 30,000 feet to, say, 10,000 feet. But he's flying it parallel to the ground, and intimating that sometime soon, it'll land. The dangers of keeping the plane at 10,000 feet still exist -- but they diminish if the plane actually lands. When will he, or a successor, finally bring the plane in?