Don't know if been raised before, but asking as at the weekend I was enjoying being out in my VX220. I spotted an Elise S2 coming the other way, whilst going through a small town centre, and gave him a wave. Nothing in return.
Could it be:
a - He wasn't watching out for a wave and didn't spot,
b - Saw me but ignored (because in a Vauxhall and may only wave to another Lotus),
c - Saw me but not the waving type,
d - Wasn't expecting a wave and caught by surprise,
e - Did respond but was too late for me to notice,
f - Suppose may have seen me but not known the relationship with our cars and just thought I was some madman waving at strangers.
I've got (admittedly not driven for a long long time but being restored) an old Beetle. When one aircooled VW driver passes another, be it Beetle, bus, Karmann Ghia etc we wave and always get acknowledgement.
Even when I had an Alfa I got the odd wave. Once a driver overtook me on the motorway and flashed their hazards as they went by. No other cars about. I thought I had done something wrong. Then realised, I'd only had the car a week, they were saying hello. They were in a 159 and me in my Brera (which I no longer own).
I do admit before getting a VX I was looking at and test driving Elises, but after driving a VX I knew that was the right one for me. No badge snobbery here.