Interesting thread.
What I have noticed around here is that I get acknowledged by just about everyone, spandex racer-types (even in small groups), pre-teen boys, joggers, tattooed tough guys on MTBs - you name it. Now I wonder why.
My theory is that I am completely unthreatening and I ride an unusual bike a lot so I have wormed my way into people's minds. I also smile a lot on the bike. Maybe they are just trying to encourage that fat old broad who obviously loves her heavy faired recumbent bike.
I also nod first. Not much, just eye contact and a nod. Maybe some people are missing the acknowledgements? They can be pretty subtle.
It could also be that I live in a friendly part of the country.
Also, if conditions are right (tailwind, downhill, bad attitude on either party's part) I can toast their cookies, so they'd better be nice.

