I think that alot of the bigger mills are USDA inspected but so are the "commercial" dealers.
The USDA licenses several hundred "commercial puppy breeders" and dealers every year. These are people who are also more commonly termed as puppy mills by some people. The license truly means nothing, it is just permission from the government to mass produce puppies to be sold enmasse to pet stores. < ---read tax dollar revenue for Uncle Sam so that makes it ok
http://www.thevoicefordogs.org/dealer.shtml