Pictured is a truck covered with LED boards displaying ads on four sides (though one of them was experiencing a technical problem). It is an effective medium especially in cities where traffic jams are expected throughout the day. I can also see that it would be valuable for services that require on-the-spot advertising in context when/where people need it rather than relying on people to take the responsibility of remembering the brand or the phone number.
The service being advertised in the truck is offering a driver for taking you home in your car when you are drunk: You avoid drunk driving, and at the same time your car is back in your garage for your use the next morning. This is, again, a socially relevant service in a culture where involuntary and social drinking is prevalent.
With so much discussion on the ecologically sustainable solutions â€“ flexible display infrastructure catches my attention nowadays.
Pictures taken in Seoul, South Korea, November 2008.