Ad space is expensive. Whether you want a billboard, a print ad, a commerical or a bus advert, you're looking at a fairly big price tag. DHL, the shipping company, decided that they'd have to find a cheaper and more effective alternative.
What they chose was to have a number of other shipping companies advertise DHL's superiority for them. How? They started by getting a bunch of really big boxes. Then they covered the entire box in thermoactive foil with the message "DHL is faster", and cooled them down to appear black. As the other companies delivered these parcels to addresses deliberately hard to find, the foil warmed up to display the colourful message.
A clear victory for DHL, even if one company tried to cover up this issue with some festive parcel tape. Check out the video of the awesome marketing campaign. I'm sold.
Ari Carrington