Thinking about this more, I think that those of you who said that people (probably myself included) are just more likely to acknowledge those who we consider to be one of us.

I guess it was just a different experience for me to nod to cyclists and be ignored, when I am used to getting a response. Basically, out of habit, I was acknowledging those who I considered to be like me (roadies, and especially roadies wearing team kits that I recognize and personally know their teammates), but given my equipment that day, they didn't equate me with their group.

Hmm, wonder how I would be treated if I were wearing my team kit while on a beater bike. That might confuse some fellow roadies out there :-)