I usually thank the bus driver, just with a "Thanks". Mind you, in Cardiff, they come in for a lot of abuse including being stoned and shot, so I feel sorry for them.
I have more contact with bus drivers than is good... too much public transport usage! And a "cheers" or "thanks" usually suffices, 'cause generally they're very moody. I've only ever met one nice one, and he was actually a scheduler/office worker or summat who'd been drafted in to drive the last bus of the day. Still, he gave me a lift about 8 miles off-route and didn't crash into anything, so I'm not complaining.
I once got on a local bus in Pontypridd, driven by the usual driver, who was very nice ordinarily. Unfortunately he had just broken up with his girlfriend and seemed to have a deathwish - as we drove along some roads with very steep drops without stopping the whole trip it was a wee bit scary..
In Edinburgh the whole 'to-thank-or-not-to-thank' dilemma is solved by having exit doors in the middle of the bus. Communication with the drivers seems to be strictly discouraged, in fact, by virtue of them sitting in a perspex isobooth. Your fare is poured into a slot, whereupon the driver presses a button to signal its descent down the chute of destiny into the locked safe of eternity (they don't, famously, give change). The ticket appears from a hole in the wall. The whole thing works so that even eye contact with the driver is a near impossibility... I quite like it that way.
I had the eerie experience last night of travelling on a coach whose driver had the exact same name as me. I'd never met anyone else with my name before. It's decidedly creepy.
My colleagues googled me and discovered someone with my name that they claim also looks exactly like me. I dispute this (not only because he's over 50 and American). But I'm still slightly disturbed.
Someone with my name draws Harry Potter fan art. Someone else is a pop star. And another one is head of a Meat Board (?) or something, if I remember correctly. But I'm the best one. :)
Whereas I (as could a great many people I suspect) can be fairly sure that my name is unique, even if we discount my middle name. Anybody with my surname is a member of my father's-side family and due to cultural/ethnic reasons, the probability of any of them sharing my first name is extremely low.
According to google, I have one phonetic namesake (ie her name is spelled wrong) who's a successful college runner in the US. Anyone who knows me will know she's not me as I'm crap at running, whereas I am rather brilliant at writing - she doesn't have any google-indexed articles published on the Institute of Biology's website.