In ultra-polite Japan, there are people who do, believe or not, break the rules. So there is a cute campaign by Tokyo Metro to show people how not to behave. The folks who contribute to TransitFan at re:place magazine have a new article on some of these new subway ads that tell people what the boundaries.
I think one of the more interesting ones is that talking on the cell phone is highly discouraged on the train. I can attest that people do not use their phones on Tokyo trains except for text messaging. Even though it’s crowded on the train, the Japanese do expect a certain degree of quietude in the crowd.