I'll tip a taxi driver in Sydney if he knows where he's going.

Me: "Can you take us to Neutral Bay?"
Driver: "Where's that?"
Me: "It's just over the bridge."
Driver: "What bridge?"

Seriously. I've had taxis in Sydney hand me a map and ask me to navigate.

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An acquaintance of mine had a stint as a cab driver in New York, while studying art. He once picked up this couple and spent nearly an hour trying to find their destination. Finally he gave up and at their demand drove them back to their point. Yes, there was shouting, and yes expletives were hurled. And, yes, his career as a New York cabbie was very brief, indeed! :cool:
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I always toss the cabbie a few bucks, especially if he takes me straight there with out a lot of turns and loops.

My theory on tipping is pretty straight forward, I will tip very nicely pretty much all the time so I get a reputation. Then when people see me, they are nice because I generally have dollars signs following me around. You get what you pay for, simple as that.

There are the rare exceptions. But trust me, if I don't leave a tip, I'm talking to the manager as well, that's how poorly the service had to be.

Again, this is just my pet theory. I'm not a sociologist, but it seems to work for me.

And to forestall the question, do I tip people who I assume I'll never be seeing again? Yes, grandly in fact, force of habit... ;).

"You may do a tour of Sydney
But in fact it's on the cards
The place you sought
When you climbed aboard
Was up the road a hundred yards."
From an old comedy song.