USDA exposes citizen data

These data breaches at various government entities have been happening so frequently that they don't even seem all that shocking anymore. But, of course, exposure of American citizens' data is serious business, especially when it's related to those citizens' receipt of federal aid.

Since I'm not a hacker, I have to wonder: how did the private information of so many people became available to the public via the open Web? What measures are in place, or are lacking, in terms of protecting this information at the federal level? The USDA owes us an explanation.