We all say it, especially while stoned and watching the Big Lebowski--"Dude."
The Atlantic recently gave a lesson on the Brief History of Dude, which tells us that the using the word to refer to someone always implies solidarity without intimacy. In other words--hey, you're pretty cool, but it's not like we're best buds or anything, dude.
Females and homosexuals now use the word as freely as surfer bros and stoners. Women apparently use it to diffuse tension, and novelist Bret Easton Ellis would like to see more chill, laid-back gay dudes.