most likely its a scam, maybe its common in china, and they are honest(most of them) about the trade(game card fro gold, etc)

but even the player is honest about it, its still illegal(in us and euro server).

blue doesn't allowed any outside service(transfer/race change, etc) for in-game gold, maybe even rl money too, to the blues, its illegal and ban able.

http://blue.mmo-champion.com/topic/166738/...rs-key-for-gold


but the blues's virtual pets, TRH(the retarded horse aka. celestil steed), gatorade(?)' battle bots pets kinda have another rule for their own.
blue sell in-game pet for RL money.

i look it in another way,

no one likes some outsider trying to leech some money from thier product without premission.
mostly likely the large amount of gold would be turn into gold selling.
blizzard will get a bad reputation for letting gold seller rule/ruin wow.

aside from stoping gold seller for ruin the in-game economy,

if the trade is honest, the service provider get the credit(for being honest); blue may get the rl money, but player didn't think much about it.
if trade a scam, blue have to "fix" it and maybe take the blame(some player do blame the wrong side)