They wore T-shirts saying "Homeless Hotspot" and appeared in Austin during South by Southwest.
Tim Nolan with BBH says the advertising agency knew Monday's experiment could be provocative.
One homeless participant, Clarence Jones, says he did not feel exploited and was doing his job.
The volunteers were paid $20 for the day to carry devices allowing them to offer 4G Wi-Fi access, in exchange for donations that they keep. They're associated with the Austin Resource Center for the Homeless, managed by the nonprofit group Front Steps.
Front Steps official Mitchell Gibbs says the program puts a human touch on the homeless problem.
South by Southwest runs through Sunday.
