[cube13]

At one point, they were pretty protective about WoW's economy. In vanilla, there were a lot of gold sinks, like skill/spell training costs, riding skills, etc. Those are sill present, but don't impact the game nearly as much. They're mostly vanity things like gigantic bags and non-combat pets. In-game currency was relatively rare, with most endgame bosses giving less than 1 gold per person.

That changed during the middle of the Burning Crusade expansion, where Blizzard basically decided that the gold sellers won, and that they were just going to flood the market with currency. They added daily quests, which were quests that gave reputation and gold every day to top-level characters, as well as more sinks, like a character title that cost 1000 gold.

At this point, gold is basically a joke, because it's extremely easy to get with a minimal time investment. Half an hour of play can get the player anywhere between 100 and 400 gold. It appears that most of the gold sellers have moved to selling epic tradable gear and items over gold at this point.