Adept
Master Black Belt
When I was in high school, I used to shoot the bow and arrow in the back yard. I went down to the basement one day to get it out. I carried it up the stairs, and my younger brother was walking up the stairs in front of me. He didn't realize how I was holding the bow. He suddenly turned around for some reason, and took the tip of the bow straight into his eye. It was really freaky the way he started screaming. I thought he might have had some real damage. Granted, he was just a kid, not a big thug on drugs, but the affect was dramatic.
Another time, again while in high school, I was laying on the floor of the living room. My older brother lobbed a tennis ball at me, just for kicks. I didn't see it coming, and it hit me square in the groin. I can't describe the sick, painful feeling that spread thru my guts and had me doubled over.
I've also on occasion hyperextended my knee while practicing my kicks. My knee swelled up for a couple of months, and it was painful to walk.
I think that if we all think back on our lives, we have probably had some pretty convincing examples of how effective these targets can be if struck. Granted, you still need to have a good delivery and the know-how to land a good strike, and that should be practiced. Also, everyone's reaction will be different. But I don't think there is any question how effective these targets can be. We just can't deliberately practice them on each other. Practice the delivery, and trust the effects will be there if you follow thru.
One thing it is important to remember is that the injuries we take in our everyday lives catch us largely by surprise, and exponentially more devastating because of it.
I remember attempting to eject an extremely large, aggravated man by myself (in hindsight I should have waited for backup, but my ego wouldn't let me) and we got into a wrestling match on the dance-floor. I jabbed my thumb into his eye and started scrabbling around and while it loosened his grip, it was certainly no fight ender.
It was effective in that it distracted him and allowed me to take his balance, but don't count on an eye gouge or poke to be a fight ending move.