The USDA is now claiming that the NAIS (National Animal Identification System) is necessary because of Asian Avian Flu. It would is pointless, because the flu could carried by wild birds. See this article in the Seattle Times. Mike Johanns (Secretary of Agriculture and one of the major advocates of the NAIS) said, "None of us can build a cage around the United States. We have to be prepared to deal with the virus here."
The NAIS program is clearly an attempt by the big agri-corps to remove competition and open foreign markets, or if you are more conspiracy minded, a system to control the nation's food supply. Please oppose this scheme by writing to your representatives and spreading the word. See the SurvivalBlog NAIS primer, NoNAIS.org, and the USDA's NAIS page.