anybody use "wire brush" on weed trimmer?

I had a close friend who was cutting his grass, he was about 16 at the time. I noticed that his Dad ran to his son (my friend). They went to the car and left....later I found out that they had gone to the hospital. The lawn mower had hurled a piece of safety wire into my friend's foot. The piece of wire pierced his shoe and buryied itself deep into his foot. He told me later that the doctor at the emergency room grabbed the wire with a set of pliers and couldn't pull it out. He said that it hurt like hell!! They finally got the wire out of his foot but not until they had to pull extremely hard on the wire. Stuff moving at high speeds can cause great harm!!!