Vacant Storefronts Sell Space for Ads

'All you have to do is walk out the door for lunch and notice the number of vacant storefronts - and they tend to be in prime areas, in major thoroughfares, and they're unused space - so why not get in there and put a message in there?' said Peter Sherman, the managing director of BBDO West, San Francisco, part of the Omnicom Group.

BBDO West is running ads for Conservation International in storefronts in New York, San Francisco and Berkeley. Advertisers can rent the storefronts for a fraction of what landlords charge retailers.

Mr. Sherman is paying an average of $500 for three-month stints in prime locations. (An outdoor billboard in comparable spots would cost $50,000, he said.)"

"'It looks better for something to be going on in the storefront,' Mr. Sherman said. "If that something is a positive message regarding the environment, that's a win for both sides.'"