Do you greet people as you pass them?

[Miss Hepburn]

Always.

[animalcrazy]

I pretty much talk to everyone. It would be rare for me not to say hi to someone I've passed on the street. Sometimes it's just a smile if I'm talking to someone else walking with me.

[simplepeace]

Yes, unless they are looking down, or away, speaking to someone else (or busy with their kids, dogs, etc...) or looking at/ or on their phone. I too do the finger lift on country roads. If my hands are full when walking my dogs and someone waves I give a nod or a chin lift.

I find it rude if some one interrupts me while I am doing of the above. I have had it happen, and oh it is so rude to get into someone's bubble for your own gratification. Most people are not that clueless though.
At one time I knew a woman who would interrupt people out walking (and talking to their walking partner) to say hi. She thought I was rude for not doing it, but 90% of the time they would just stare at her, and keep walking, not happy either.
If someone interrupts me in that manner I do not acknowledge them at all.

[Chubby Checker]

I actually try as much as possible to ignore them. It's not necessary to greet someone you don't know. Or quite frankly, someone you DO know