Blizzard is not hunting them too valiantly, skipping even obvious ways to stop them. For example if I write the 4 letter f-word into the chat it will appear as "@#$%". On the other hand I can easily write the url of gold seller site, and it won't be "@@$#$@"-ed out, nor a GM will contact me asking to stop mentioning a cheater site. The logic behind it is obvious and truly goblin: money talks. Blizzard want subscribers and by effectively stopping gold sellers, Blizzard would lose two bunch of subscribers: the farmers themselves, who pay their monthly fee for their farm characters (except when they hack accounts). The other and bigger amount of subscribers lost are the loser players who cannot compete without cheating. It is a large playerbase. It's them to blame for the nerfs too. For the smart there is AH. For the laborous, there are dailies. For the dumb and lazy, there are cheats.
Blizzard will only stop gold selling or any other cheating method when more subscriptions are at risk because of the cheat than because of stopping it. There were two incidents when cheaters were massively punished in WoW:
- Taking arena gear from win traders. The win traders used to artificially arrange matches (for example playing 3 AM) aginst the buyer and they deliberately lost, giving arena rating to the buyer. During this operation their own team ranking went down, and they climbed back to 2000+ by ganking players at the 1500-1900 range. This behaviour made it practically impossible for legitimate inexperienced players to start performing in the arena.
- Banning 500K accounts for botting. Botters made Alterac Valley practically unplayable, since half of the team was AFK. They also made primal farming, and questing in primal-affected areas very hard since for every elemental, there were 5-8 hunters with the very intuitive pet names "boar" and "cat".
The gold sellers on the other hand are not such a risk. Just because LegoIass buys his epic mount that he could never gain legitimately, you don't lose anything. Consumables are not usable, BoE items are not convenient in arenas, so no player will lose arena rating because of the illegal income of LegoIass. A hoard of gold allows you to gear up a new lvl 70 for raiding and save a raider from farming consumables. But instance and raid bosses are in unlimited supply due to the instancing, just because LegoIass downed Prince in his full cheated epic gear, you can still down yours.
I think, the BoP system is created exactly to decrease the effect of gold selling. No matter how much gold you have, in order to get your Warglaive you still must down Illidan. Maybe money can buy your way into the raid, but you still has to kill Illidan and hope it drops. So noone will leave just because "you can't outgear a cheater". You can.
So gold buying is a victimless crime, so Blizzard will keep on tolerating it. But of course there is no such thing as victimless crime. In case of gold selling, the victim is the economy. Why? Let's see the act of gold selling from the point of view of the characters. Wtrekwer with his loyal companion, Boar on his side walks to LegoIass and gives him 2000G and goes back to Shadowmoon Valley to keep on farming primals. Does it make any sense? Of course it does if we consider the transaction of IRL money between the player and the farmer company, but in the game world, Wtrekwer is simply extremely stupid.
Wtrekwer keeps on flooding the AH with primals pushing down their price while LegoIass will pay any money for BoE epics, skyrocketing their price. They are both doing something they would or could not do if there were no gold-selling.
Of course someone following the goblin way can adapt to these effects. You can traffic with BoE epics keeping their price irrationally high, since LegoIass can pay. You can get really rich this way. The problem is exactly this. LegoIass is way too dumb to make any logical choice, making our way to gold too easy. LegoIass is to blame that simple AH-sharking (when you just buy and resell and provide no service) is so effective. Too easy = boring. Too easy = you learn nothing.
I'm not preaching to avoid dealing on these markets because of LegoIass. To skip an opportunity because of moral reasons are not the goblin way. But keep in mind that there are other, real-business opportunities out there that can make you rich. Don't forget, anyone with Auctioneer can find LegoIass and undercut you. On the LegoIass-market you are not the only shark. The invisible hand of gold is still at work!