I do not think that sharing food from my own plate is a HORRIBLE thing. Well, if the other person doesn't touch your plate or dirt it.
You know, I'll say more; I don't think that a person can't take food with the hand from your plate (if she do it with your permisio), if you know that the other person has cleaned his hands, whats the matter?
In fact in some cultures it's a normal thing to eat in a group (like here) and to share the food from a single plate per each type of food, all this with the hands!
So, having said all this stuff, can somebody tell me what's the problem with sharing food?