I never used to have a problem with cabbies, until one broadsided my truck while he was driving on the wrong side of the road. Remember that the "professional driver", who is behind the wheel, may be no such thing. If a taxi isn't being used, it isn't making money, so someone's brother's best friend's neighbour might be the one behind the wheel.
Had one trying to race me, from light to light, this morning. I have no idea why but, as I was leaving him behind with my normal acceleration and the road was pretty much empty, I didn't worry about it. Normally I would have held back and just let him go, because it's easier to keep track of bad drivers who are in front of you, than behind you.
Behaviour, that I have observed from cabbies:
- "U-turn of death" (well described, RetroGrouch)
- straddling the line, during rush hour
- dropping fares into traffic
- illegal left and right turns, at signed intersections
- turns from the wrong lane
- driving at 20 under the limit, while on the phone or reading
- parking for extended periods, in no parking zones, during rush hour
- driving the wrong way, down a one-way street
Also worth watching out for are tow trucks (already mentioned) and plain white vans.