Oh, and yeah, I didn't mean that I expect everyone to start a chat, yeah most of us are probably not up to any chatting in the morning but I see nothing wrong with saying "hello", raising or waving a hand. A quick nod is also enough. Also, this applies usually to situations where there is fewer cyclists: you see another guy on a bike and greet him. If you're in a busy bike lane then it's simply impractical and perhaps unsafe to greet everyone