Ok, so the first guy we tried to do business with--the shuttle driver at the airport--was a total ass who tried to charge us double the normal fare, but apart from him, we've only dealt with super nice people.
Want pushy street vendors who won't take no for an answer? Go to Antananarive. The residents of Madagascar's capital win that competition hands down.
Want rude toursism agents and agencies? Go to Peru and Bolivia where they believe a sucker is born every minute and they have no need of a good reputation or repeat business.
In Vietnam, people care about their image and they care about word of mouth, at least those we've had contact with do.