The crack of splitting waribashi, wooden disposable chopsticks, has marked the beginning of restaurant meals in Japan since the eighteenth century. Considering Japan now tosses out 25 billion pairs of waribashi every year, that's a mind-boggling history of what seems to be unnecessary waste.
Even the most elegant, expensive restaurants use waribashi, which seems a bit incongruous to non-Japanese eyes, like a fancy French restaurant handing out plastic-wrapped spork, knife and napkin sets. But the rampant use of waribashi is actually based on a deep-rooted religious belief which prevents the sharing of chopsticks with another person. Shinto has among its many concepts of defilement and purification the belief that anything which touches a person's mouth carries with it a bit of that person's character and if used by another person, could pass on a spiritual contamination that no amount of Listerine could ever wash away. Even within families, each person has their personal pair of chopsticks. You might say sharing chopsticks is like sharing underwear; no matter how thoroughly washed they were by the previous owner, it would never feel quite right.
So how to avoid contributing to the growing mountain of trashed waribashi every year while maintaining a spiritually pristine mouth? Carry your own chopsticks in a chopstick case! The one I use is small and imprinted with rabbits, but there are other, less girly versions available, like this slide-top box.
A final note about waribashi etiquette: it is considered somewhat rude to rub the freshly-broken chopsticks together because it implies that the waribashi are cheap and, therefore, that the restaurant is cheap. But a final note about chopstick etiquette: there are approximately one thousand ways to handle chopsticks in a way that is considered rude.
"there are approximately one thousand ways to handle chopsticks in a way that is considered rude."
Encouraging. :P