The Federal Trade Commission will investigate Apple's marketing of iOS games with in-app purchases to children. The decision comes after a wave of complaints about kids running up huge bills on their parents' iTunes accounts. FTC Chairman Jon Leibowitz acknowledged in a letter to US Rep. Edward Markey (D-MA) that the FTC shares his concern over the phenomenon, saying the Commission would dig deeper into it.

Stories about children inadvertently spending thousands of dollars inside of their parents' iPhone apps have circulated around the Web over the last year or so, but have picked up recently thanks to a new wave of mainstream coverage. Markey had written an open letter (PDF) to the FTC last week over Apple's (and Google's) use of in-app purchases to sell gaming add-ons to kids, saying that he was "disturbed" by the reports.

"Companies shouldn’t be able to use Smurfs and snowflakes and zoos as online ATMs pulling money from the pockets of unsuspecting parents," Markey said in a statement accompanying his letter.

The FTC apparently agreed with Markey's concern and has opened an official investigation into the matter. "We fully share your concern that consumers, particularly children, are unlikely to understand the ramifications of these types of purchases," Leibowitz wrote in a letter back to Markey, as quoted by the Washington Post. "Let me assure you we will look closely at the current industry practice with respect to the marketing and delivery of these types of applications."

Parents are able to turn off in-app purchases completely on their iOS devices by going into Settings > General > Restrictions. Still, this isn't an ideal solution for adults who like to make their own in-app purchases, but "share" an iPhone with a kid.

Apple hasn't formally commented about the situation yet, but reports circulated earlier this week that Apple had "strong words" with Capcom over possible legal problems with its Smurfs' Village app. This isn't the only app that kids have gone crazy with, though—any game that allows for in-app purchases can be taken advantage of for 15 minutes after a parent enters his or her iTunes password. (One friend of ours mentioned that his third-grader ran up a $500 tab from a single game.) We wouldn't be surprised to see Apple significantly shorten that in-app purchase window in the near future, or add a setting that lets users decide how often they want to enter passwords for purchases.