[cm42]

I'm apparently in a minority here, but I've only known one guy to use it as a term of address (vs. how I just used it), and he notably did it with everyone, a la "dude" (so much that "Guy" became his nickname).

Chief, on the other hand, I've only heard directed at males.

[zoklet-enjoyer]

I don't know about the rest of the country, but in ND and MN everyone uses "guys" to refer to any gendered group of people

[cm42]

Yeah, I grew up in PA and that's pretty common there, but when talking to one person, it's usually "Hey dude" or "Hey man" (also mostly gender-agnostic)

Only that one guy would use it for one person, sometimes similar to whatchamacallit: "Guy! Whaddareya doin up there?!" "C'mon, guy! We're gonna be late!" "Any of you guys see my toolbox? Did guy take it again?" (Which guy, man? Dude, there's like ten guys here. Bro, you gotta be more specific.)

[jkaptur]

I think this is really interesting - I've heard "guys" used to address a group of mixed genders ("how are you guys?") but it sounds much more gendered when used to refer to a group ("how many guys are in there?" or even "are you looking for those guys?").

[JamesianP]

Perhaps because addressing people comes with more implications and possible angles for communication with those people. So "guys" fits the bill for one desired nuance that became more popular in culture (the "laid back" nuances the article mentions). Previous generations were a lot more formal.

[the_gipsy]

Obliviousness doesn't make it right.