Ads on billboards and subways actually bother me far more than search ads.

It's visual and cognitive pollution on public space that I've never consented to - I find it viscerally offensive.

We don't accept billboards on hiking trails, or in elementary classrooms, or in courtrooms (as far as I'm aware, though I wouldn't be surprised if someone turns up a real-life grotesque examples) - we shouldn't accept them in other public spaces either.