Valve opened a photo-submission contest offering beta keys for DotA 2 and asking fans to show just how much they want one. The contest guidelines included the requirement that images be larger than 600 by 400 pixels. Think a billboard will do?
Steven Addison talked a rep for Clear Channel, owner of this digital billboard in his neighborhood, into displaying this image for a brief time for free. There are many creative and, well, uncomfortable submissions in the official forum thread. If any of these could get someone a key, Addison's should do it.