After reading a billion articles and such, I write up a summary of everything I had read for my FB debate. Thought it might be helpful here, too, since this doesn't seem to be coming clear for everyone:
Corporate butchers still use knives to cut meat from dead things. You don't just tap a cow and suddenly it falls apart into steaks. When cutting the meat, since a human is doing it, there is going to be some left clinging to the fat - as the sites say, just like when you cut the fat off your steak at home. You will ALWAYS be throwing some meat away. So, corporations see this, and they're like, crap, we're *throwing away* tons of meat. But there wasn't anything that could be done about it for some time; because there simply wasn't a better way to get meat from a cow other than cutting.
So then a process was developed by which that meat would not go to waste - putting the fat and meat in a centrifuge at low heat in order to separate it. Just like if you had a basket of chaff and wheat, and spun in a circle, causing the chaff to fly out.
There's a catch, though - when you heat up meat just a little bit, blammo, suddenly you have bacteria. Because of this, the process includes a step where a puff of ammonia is sprayed on the meat to kill the bacteria. When combined with the water in the meat, the ammonia becomes ammonium hydroxide - a substance that is safe, has been used in food since 1974, occurs naturally in the human body, and is used in other foods you have no problems consuming - other foods that suffer from the same issue (heat making it easier for bacteria to multiply). One of these substances is chocolate.
The stores that are bragging about not using 'pink slime'? It's a ridiculous brag. What they're saying is that they are LESS technologically developed than other companies; that they grind their own meat and have yet to figure out what to do about the fact that they're throwing food away. Think about the terms they are using - a gross-sounding term that is actually meaningless.
And if it's ammonium hydroxide you're worried about for some reason? Please note that the companies (Whole Foods, Target, etc.) never say they're not using that. What they say is that they're not using 'pink slime'.