Hi! I think Cheapskate is my long lost twin. I don't eat much and most meals are way too much for me to finish in one sitting, which is why my nickname is "Midnight 'Doggy bag' Kitty." When I am in a situation where I can't do the doggy bag routine, I order an appetiser or salad to be served with everyone else's dinner. DH usually lets me have a couple bites of whatever he's having. Last time I did this, we were dining with 2 other people. Both of them gave me something off their plates, too. One said, "I can't eat both pieces of bread. Would you like one?" I left after eating a sufficient amount of food and minimized the amount that was thrown out. Win - win 
It's win-win if the people eating with you *really* don't want the extra food. However, if you're sitting there with two scoops of salad, staring wistfully at everyone else's Lobster Newburg, until they fork over part of their meal out of guilt, it's only a win for you. It's a loss (in food plus enjoyment) for everyone else.
I'd say if you're looking so hungry that someone is passing over their bread, you just might be overdoing it. And if you are not full until three other people provide you with part of their own dinners, you were hungry enough you could have eaten your own meal.
That's an interesting assumption. Actually, you made several "interesting assumptions" which were disparaging of my character.

You describe me as a cheapskate, drooling over other people's plates until I guilt them into forking over part of their meal while they go home hungry, when you don't know me and you weren't there.
I was not "staring wistfully" at anyone's meal. The restaurant serves humongous meals. I knew that, but the people with whom I was dining did not, so they ordered about twice as much food as they thought they were going to get. It was as they were ordering that I realized that we were going to have enough food for an army. In addition, they were buying, not me. They asked me if I wanted a meal and I said, "Nope. We're gonna have choke grinds already."
The person who gave me the bread is on a low carb diet, so their bread was going to waste if I didn't eat it. My husband gave me one of his three pieces of chicken, which is how we always split our food (2 parts to him, 1 part to me). The third person asked if I had tried the pulled pork because it was "broke da mouth," so I tried a bite of that, too.
DH & I dine with other "foodie" couples. We'll order as a table and share all the dishes. This was the first time we dined with this couple and we all agreed that, in the future, we are going to dispense with ordering individual meals and "buy for the table" instead.
I gotta say, Twik, this post of yours has changed my opinion of you since it said a lot more about your presumptions than my eating habits.