@shadowcat: it varies per location, in many cities if not outright illegal it can be at least against the Taxi Regulations to refuse a legitimate fare, save for some specific exceptions. In a few places it's still "we reserve the right... "
As for SC trips, a fair strategy, if you can determine the area is relatively safe, is to identify an address down the block/across the street within walking distance and ask to be dropped off THERE rather than "take me to The Tit Parade". On the return trip you can probably tip the barman/doorman to call you a cab that has no objection to pick you up there.