I suppose this is one way to keep your respondents engaged and paying attention:
It might just be that I’m looking at this relatively early in the morning — maybe some additional coffee would help — but this seems like a yes/no radio button situation to me — either I saw an outdoor poster or I didn’t. Maybe they’re expecting people will type in the exact location where they saw the advertisements? That must be it, though they don’t explictly say so. And I wonder how useful those responses will be to them — what can you do with “on channel 3″ in the “on the television” box?