> The question is where on the spectrum to advertisements fall: they're not obscene, but they also not harmless. They have a measurable effect on people, maybe

> The question is where on the spectrum to advertisements fall: they're not obscene, but they also not harmless. They have a measurable effect on people, maybe informative, maybe harmful. Exactly. And the only ways our society could agree an advertisement is harmful is if it 1. was fraudulent, as I said or 2. was obscene/offensive/hateful (see: fighting words category of exceptions to first amendment). However, the OP seemed to think billboards are externalities in and of themselves just because he didn't want to be influenced by any information.