Personally, everytime I walk with my friends on my way to the city centre or something, we always get this kind of frightened scared look given to us by some adults (not all, just some). Its really weird because, we are not like some "weirdos" walking around and threatening people or anything. We are just minding our own business and going somewhere to relax.
I still can't get my head round the reason why some people are scared of teenagers.