I always thought 'dang' was the american way of saying 'damn'. Even if I am mistaken, both of these words are not very dirty words at all... that's why they are more commonly used in public.

What has been already is true, but I thought that it was a very old fashioned expression.

People say "dang" when they don't want to curse. Like Peachey said- you say it instead of damn. It's a very common word in the Southern United States.

"Dang!" is a softer way of saying "damn!" "My computer is now a pile of ash, and I can't log in to italki! Dang!" It makes me think of Wild West movies. ^^