I checked with my partner's son (age 21), and he says that "buddy" is making a comeback in his age group. "Nice and retro," he says. His restrictions: he'd never address a woman as "buddy," and it's not used for close friends. It's mostly for acquaintances he might like to see again -- "Yeah, buddy, nice to meet you; we'll have to get together."

Now whether this trend has spread beyond his university, I don't know. But it's interesting.