"Some privately run Minecraft servers do charge for in-game items, for xp boosts, for access to certain game modes. Some of them even charge quite a lot," Minecraft creator Markus "Notch" Persson wrote in a new blog post yesterday. "I don't even know how many emails we've gotten from parents, asking for their hundred dollars back their kid spent on an item pack on a server we have no control over."
To help protect from such accusations in the future, Mojang has created new rules regarding monetization. The rules have been detailed on Mojang's site, but what it boils down to is fewer restrictions on creating and selling in-game items and other monetized goods. Just make sure to communicate with your customers that you aren't Mojang, don't sell items that impact gameplay, and don't charge real-world money for in-game money.
Oh, and one last thing, a request straight from Persson: "Herobrine is not real please stop asking."