Though online games like World of Warcraft have gotten plenty of bad press for being “addictive,” at least the financial ramifications are limited to $14.99 a month – well, unless you (a) lose your job because you play too much, or (b) break the game’s TOS and pay for your gold.

So what about the new craze of casual games, particularly the ones played on Facebook, that aren’t pay-per-month but rather pay-for-content? You may recall that there have been some issues with scam advertisers in Farmville and other Zynga games, a side effect of the business model that allows players to earn coins to purchase content by signing up for free trials from advertisers. But another way of getting more and more Farmville stuff (like land, crops, animals, etc.) is just to pay for it – e.g., $5 for 7,500 coins.

But how much virtual farming goods could you possibly buy in a couple of weeks? Try £900 – or about $1400 USD. A UK woman discovered last month that her 12-year-old son first emptied his own savings to pay for about a third of that, and then ran up the rest of the debt on her credit card. And this was only in about two weeks, starting on March 14 and going on until the end of the month when the mom discovered the charges.

Unsurprisingly, there isn’t much the mom can do about it, since the only way she would be able to get her money back from the credit card company would be to report it stolen (and I guess she doesn’t think her son deserves that hard of a lesson). Facebook suspended the kid’s account, and Zynga helpfully suggested she try using passwords on her computer.

It was unclear from the media report whether the kid stole his mom’s credit card without her knowledge or if he’d just used it for something she hadn’t given him permission for – I’d assume the former, since giving a 12-year-old a credit card number doesn’t seem like a great idea. And speaking of his age, it is actually against Facebook’s TOS for anyone under 13 to have an account.

Whether this says something about Zynga’s business practices in general, I suppose it serves as a cautionary tale to parents. Kids (typically) don’t have a great head for finances, especially when what you’re buying is virtual – heck, there are plenty of adults playing games like Farmville that find themselves surprised by how much it costs. And this kid’s reason for spending so much? “They had brought out good stuff that I wanted.”