Skimmed the New York Times at the Bro-in-laws house in Wisconsin a couple of days ago, and came across this. Beef Products Inc. supplies burger to McD's And Burger King. They wanted to add more fat and garbage cuts to their blend, but fat carries a higher risk of contamination. So they came up with a process of treating their meat with ammonia, which supposedly tested out as very effective. More recently, a substantial amount of contamination has (at least allegedly) been found in their product anyhow.
My reaction is not so much fear of disease from bacteria in the stuff, as it is finding this about as appealing as the (spurious, as it turned out) Chinese burger-and-cardboard story from a while back.
There can't be much if any ammonia residue; the stuff smells too strong to conceal. But, sheeesh.