I would, and once I get my shirt I would wear it or not, depending on what's in the back, my advise to you would be to allow people ordering the shirts to pick what company or design they'll have in the back, I might have a problem wearing merchandise of companies that don't sit well with my lifestyle (e.g. as a vegetarian, I wouldn't wear the shirt of a company that primarily sells meat, like McDonald's).

Offering the people that are wearing the shirts a mix of back designs (say, three different ad designs to pick from for Whole Foods or any other advertiser) would be a plus to improve adoption.