I would cut people some slack as well. I'm not sure about your area, but there are an abundace of cyclists around here. After seeing multiple threads on this and other boards about this same topic I decided to count the number of cyclists that I encountered one night. The ride was about 28 miles, with part of it being on the road and part on a dedicated bike/walk trail. I counted about 200 cyclists coming towards me that night. I didn't even count those that I passed. I did not wave or say hi to each and every one of them and I really don't think that makes me a snobby roadie. I will certainly reciprocate if someone waves and I if I see someone with a mechanical problem I will ask if they need any help, but I honestly don't think that I need to personally greet all 200 or so folks that I see in an hour and a half's ride even if we do share the commonality of riding a bike.