As a dark matter of fact

I heard a decent Science Friday podcast about String Theroy (audio link) where one of the guests suggests that it's a bunch of mathmatical hooey. I have actually heard the same from physicist graduatuate students. The real problem seems to be that after a very long time fooling around with mathmatical models there still is no experimental evidence for the theory. As I understand it, there are not that many testable predictions that the theory makes.
Blows my mind also that apparently researchers have just finally found proof of dark matter. Wow. The dark matter guys have much better PR or something. I thought dark matter was fact and already proven by observation.