I make it a point to be known by the folks I pass on my commute. Commuting is different than most cycling because you meet the same people every day, and since a cyclist is a bit of an oddity, they'll get to recognize you. So, I prefer that they remember me in a positive way, and greet folks in a friendly way. Over the years this has not only made the commute nicer and created a sense of community along the 6 mile strip, it's also paid off when I might have needed help.
I've had a bus pull over and ask if I needed a ride while fixing a flat in the rain. Also, fixing a flat (all my flats are in the rain or cold, I've yet to flat in balmy weather) on a cold winter day, a cop stopped and told me he couldn't give me a lift, but if I wanted to warm up, I could sit in his back seat while he did some paperwork.
So, I'm with the OP on his policy of saying hello, but I'd stop trying with folks who don't respond, since there's a difference between being sociable and being a jerk.
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Chain-L site
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WARNING, I'm from New York. Thin skinned people should maintain safe distance.