Yech, here's one more reason to either not eat industrially-produced beef, or to stick to grass-fed locally raised beef.
Last summer Topps Meat had to recall almost 22 million pounds of beef after more than 40 people got sick from eating e coli hamburgers. Mmm, uninspected meat. Now it turns out the company was only testing its meat 3 times a year, and, according to the NY Times, "untested meat boxes from the freezer were tossed in with the daily grind, as were untested scraps from the plant's steak line."
I know part of the appeal of hamburgers is that they are a huge convenience -- especially if you are just taking the patties out of the freezer and throwing them on the grill -- but, it's pretty disgusting to think about a patty that might contain bits of meat from hundreds of cows, which were raised and slaughtered until filthy conditions. Which is not to say that I don't love burgers. I just want the meat to be well-raised and properly-processed.
If you want to be really safe, it's not that hard to grind the meat yourself, and it's much safer.
Here's what you do: buy a sirloin steak, or London broil, or some other cut that is not that expensive, but from a grass-fed farm. (Yeah, they won't be a buck-a-patty, but that's what sets you and your famous hamburgers apart from everything that is gross about McDonald's.)
Cut the meat into chunks. Put it in the food processor and press pulse. When it's just barely ground, form into patties and cook. Based on everything I have ever read, your chances of getting e coli poisoning and mad cow disease just dropped drastically. And, they will be the best burgers you've ever had. And the safest.