Mobile Phones in Tokyo's Subways
Text messaging is extremely popular in Tokyo for lots of reasons. First, it's cheaper than making a voice call. If you message someone in the same network, it's totally free.
Second, it's considered extremely rude to talk on the phone while in certain public places - like subways. In other places, it's against the law. So people have to resort to text messaging.
While waiting for a subway, you'll see legions of people whip out their mobile phones and start text messaging.