A concerned reader alerted me to some changes in Wizard101, which introduces an arena including the option to place bets on the outcome of the matches there. Now Wizard101 is usually an extremely child-safe game, with a safe chat system and everything. So having gambling in that game raises an eyebrow.
On the other hand most games, even child-safe ones, have some elements of chance. While there is no gambling, strictly speaking, in World of Warcraft, you are taking a gamble every time you, for example, go for a raid and hope for an epic drop for your character. Many loot systems are specifically designed to use dice rolls to resolve issues of who gets an item. Would betting some gold pieces on an arena event be much worse than that? I'd have more concerns that betting on a PvP event could be too easily manipulated than it being a slippery slope to children getting addicted to internet gambling. What do you think?