I have such strong startle reflexes that someone doing that to me might cause bad results for one of us, probably me but who knows? I was talking to a couple of friends one night and a guy came up behind me and put his arms around me partially pinning my arms. Luckily it was someone I didn't care for anyway because as son as he touched me, I automatically jammed my elbow back into his gut. He laid on the floor until he caught his breath and asked what happened, and I told him that you should never touch me without permission. He said, "Well, you could have given me a warning!" and I just told him that was a warning. Funny thing, he never tried to grab me again.