When we first arrived in Korea we found it odd to order food as a group (although we are never responsible for ordering and rarely given a choice when dinning with Koreans). At the dinning table everyone shares the food, which is great as you get to sample many dishes (IF there are a variety of dishes available, many restaurants specialise).
However, the sharing in Korea goes beyond just eating out. They literally share everything, its quite lovely at times and fairly confusing at others.
There are numerous stories told by foreigners here about being unsure if it was OK to eat by themselves when they had taken an apple to school as part of lunch, as you feel obliged to take an entire bag of apples.
Also, if you do take food into school and leave it in a communal area, say an office fridge, its likely it will be gone upon your return. This perceived minor theft by us foreigners is a great example of cultural differences. The week before the people who ate your goods probably stocked the fridge for you to enjoy too, only you had assumed that food 'belonged' to someone and steered clear based on your own morals. Who's the better man?
It is still pretty weird when people start helping themselves to 'your' things.
On school trips students back packs are crammed full of sugary snacks, enough to feed a family and well, thats their purpose. The students share their snacks throughout the day with friends and teachers- I love school trips! The students parents also provide an unimaginable amount of food and drinks for teachers too. Glorious!
The Korean mindset to share to such a great degree leaves us foreigners often in a state of perplexity. Should we share the one orange we brought for lunch with the 7 other teachers in the office (who's name you may not even know and have probably only exchanged daily greetings for the past 6 months) or should we gobble it up as its part of our lunch as the school lunch of seaweed soup and rice you just ate did not suffice?!?
I discussed this with some teachers during our field trip and they assured me they sometimes get confused with it all too, but always end up sharing. My co-teacher told me the principle of sharing all you have is based on a prophecy:
"If you have just one bean, that too must be shared."
Another explanation as to why everything here is sold in bulk. I had better start stocking up!