This is a very hot topic. Currently, there is a bankruptcy case in the District of Delaware and the company that is in view is AFA Foods (No: 12-11128.), which produces "pink slime." A little history would be helpful.
In 2002 the term, "pink slime" was coined by microbiologist, Gerald Zirnstein, who worked for the USDA. However, recently it gained great traction by Jamie Oliver, a celebrity chef, who railed against this meat.
"Pink Slime" comes from scraps of meat after the cow is cut for the best parts. The bits of meat then are heated and through machines the fat is taken away. After this, ammonia is used to kill any bacteria that might be present. At times some sort of filler is added to make the meat leaner. The FDA has stated that this meat is safe for consumption. From this perspective, we can say that it is safe. It has been consumed for a long time now.
However, when it comes to health, it is pretty clear that it is not healthy. It cannot be a good thing that amnonia is used to kill bacteria. Moreover, we need to keep in mind that the meat is the worst cuts. So, in the end, you won't get sick from eating it, but it does not give the nutrients that a person needs.