Entrepreneurs armed with little more than a URL and a pair of gloves are taking advantage of what would otherwise be an expensive media purchase. Chancers like playstickball.com are etching their messages into the disgusting layer of soot/scum/pollution that forms on the delivery vehicles that service our urban areas and thereby occupying some premium advertising real-estate. Who knows whether it's legal or not, but it's certainly an effective way of putting your product or service in front of millions of people without blowing your marketing budget!