One of the latest, and IMHO, lamest defenses of String Theory seems to be post empiricism - the notion that physics may not need all that experiment stuff. Peter Woit has an article on the subject at Scientia Salon and also on his blog. The comments are only on Scientia Salon, with the result that they are more plentiful, but to my mind, of much lower quality than usually found on the blog.
It's a real problem for fundamental physics that particle physics experiments may have run their course, at least for a generation or two. If the upgraded beam LHC sees nothing but a generic Standard Model, it may be tough to persuade governments to fund a next generation collider.
At the moment, there are two deep fundamentally unexplained phenomena in physics: dark matter and dark energy. Particle physics seems likely to have something to say about dark matter, but who knows? In the most pessimistic case, we may be approaching the limits of what a civilization of our scope can learn about the nature of the universe at the most fundamental level.
If so, post empiricism seems like a pretty bleak alternative - sending us back to the times of the ancient Greek philosophers.