I wrapped a movie called 'Zombieland,' in which I was constantly under assault by zombies, then flew to New York, still very much in character. With my daughter at the airport I was startled by a paparazzo, who I quite understandably mistook for a zombie.
A quick search turned up a rather muddled video of the incident, obviously beginning after the "zombie identification" took place. It's not clear to me whether the cameraman drew Harrelson into the incident by groaning, walking stiffly, and feigning a hunger for human flesh. But judging by the fact that no one seemed to step in and protect the cameraman, I would venture to guess that everyone else thought he was a zombie too.
As a general zombie-related panic spreads through the population, I think it's only safe to say that we might end up seeing many more unfortunate incidents like this one. A potentially worrying possibility is that people will begin to use the "zombie defense" in situations where they really didn't think that their victim was a zombie, and just wanted to attack them for other reasons.