According to a recent post in the World of Warcraft forums by community manager Ornyx, Blizzard have been cracking down on accounts who have been participating in clearing raids for real-world money.
Its also worth noting, as the post points out, that selling items, PvP rating, achievements and any other kind of in-game benefits in exchange for real currency is strictly against the rules, though they can be exchanged for in-game gold.
Finally, players should be made aware of brokers, who offer match buyers with service-providers. These brokers will take real currency from a player, whilst passing gold onto a guild or group who will provide the service itself. You can help Blizzard’s mission to eradicate this behaviour by reporting any signs of this as soon as you see it. To read the full statement from community manager Ornyx, head over to the official World of Warcraft forums for more information and join in the conversation.