What is happening is this, the gov't is buying so much ammo due to the wars, that ammo manufacturers are switching over production to military ammo manufacturing as the profit margin is great filling gov't contracts than it is selling in the retail market. So, they are going for the profit, understandably as they are a profit seeking industry.
By the way, if this ammo shortage is new to you, all I can say is "welcome to March, 2009 when most people were discovering it. If you really want ammo, you can get it on gunbroker. Most online ammo sales companies are sold out of the popular pistol cartridges.