This discussion seems to come up rather often these days. I have to say NO- if someone does not wave at you does not make them a snob. I think that it is as unreasonable to expect that every other cyclist on the road/path acknowledge you as it would be to expect every other person on the sidewalk or in a car to acknowledge you when you are using the same mode of transportation as they are.
Everyone is out there for their own reason. They may be wrapped up in thought, they may be working hard, they may just be shy, they might be afraid to take their hands off the bars to wave. They might just be wondering who is that waving- do I know them?
Personally I don't acknowledge every other cyclist on the road. It has nothing to do with what they are riding, how they are dressed etc. If someone waves to me I do my best to acknowledge them back, but we have thousands of cyclists maybe hundreds of thousands around here. I don't consider them all my personal friends just because we all ride bikes. If that makes me a snob, well then I'm a snob, but I hope that people don't judge me based on a second of passing on the street.