It is called Bumvertising.
Bumvertising™, or the use of sign holding vagrants to advertise, is a development of PokerFaceBook.com’s
most recent advertising campaign. Homeless men are able to provide a
valuable and tangible service to a company, while receiving an
additional revenue stream in combination with their normal donations
Through his own effort and the assistance of his marketing team, Mr.
Rogovy developed signs and accumulated the resources that most bums
would find attractive. Money, sandwiches, chips, apples, water, and
other beverages have all been dispensed in order to compensate the
homeless in the Seattle Bumvertising™ campaign.
I have no direct information on how real this practice is, or if it violates minimum wage laws, but the web site appears legitimate. Thanks to Curt Gardner for the pointer. Comments are open if you know more.