Kids are taught this at home, at daycare, in school.
I agree that it is important. I want my children to share with others, to be kind and caring, to know how to get along with people.
BUT...sometimes, I don't think sharing is always necessary.
Those that are familiar with my blog know that I have a home daycare. Other children are coming into my house everyday. My children have learned to share because of this. Basically they are sharing all of their toys, their mom, and their home EVERYDAY.
So sometimes I tell them that they don't have to share everything. If they just got a new doll for their birthday, they don't have to let everyone play with it. I just tell them to be nice about it or keep it up in their room. (Even though the 3 year old isn't always nice about it, but we are trying). And don't get me wrong, I don't tell my kids that they can hoard all the toys and not let anyone touch them. On the contrary, I am always telling them that they need to take turns and give others a chance. But I do let them kindly take their special stuff and put it somewhere it will not get disturbed.
The other day I went to lunch at my 6 year old's school. I brought her a soft pretzel. One of her friends asked her for some and she looked to me for the answer. I told her, "Sure, if you want to break off a piece and give it to her, that's fine." But it was her choice. I am sorry but I am not going to make her share her food. That night I told her if a friend asks her for something from her lunch, she doesn't HAVE to share. As a matter of fact, a friend of mine said her son's school has a "no lunch sharing" policy. I LOVE that!
Kids need to learn that we don't have to share everything, all the time. As long as you are polite, you can let someone know that you are not going to share a certain item.
I mean, when we get older, we learn how to do this. Don't we? We don't sit with coworkers and ask for a bite of their lunch, or if we can play a game on their cell phone, or if we can try out their new lipstick. We just don't do it. So in my opinion, if I teach my kids this skill now, they are just prepared for the future.
As adults, we tell people to eff off politely everyday. Kids can learn that, too.