From NYTimes.com: Company's Record on Beef Treatment Questioned

The company, Beef Products Inc., had been looking to expand into the hamburger business with a product made from beef that included fatty trimmings the industry once relegated to pet food and cooking oil. The trimmings were particularly susceptible to contamination, but a study commissioned by the company showed that the ammonia process would kill E. coli as well as salmonella.
...
With the U.S.D.A.'s stamp of approval, the company's processed beef has become a mainstay in America's hamburgers. McDonald's, Burger King and other fast-food giants use it as a component in ground beef, as do grocery chains. The federal school lunch program used an estimated 5.5 million pounds of the processed beef last year alone.

Using ammonia in beef sounds bad enough, but the article goes on to say that it might not be as effective as the FDA thought it might be.  I'm beginning to wonder if you can ever trust what is in ground beef.