Just a guess tmark, but two major reasons. One is the Obama scare. Ignore what he promises, he and his fellow anti gun pals like Pelosi, Biden, Holder, etc all hate guns (in private hands) and they ARE going to come after them and ammo as well. Two is recent carbine sales. When you consider the thousands of carbines already out there for years, then add another 60 thousand plus from CMPicon sales in the last few years, there is a huge demand for ammo to feed them. If you hand load, stock up on components while you still can. I have set up to cast bullets. If you don't hand load, now is a great time to start. Of the two factors, I believe the quite well founded Obama scare is the major cause of the shortage and wild price increases.
Just my humble opinion.
Best to all..
Ed