It appears according to a report from The Next Web that the iPhone App Store has been hacked and so have accounts. According to the article:
The rankings in the books category of the US iTunes store features 40 out of 50 apps by the same app developer, Thuat Nguyen.
It seems the developer in question which has apps which are being mass purchased by iTunes accounts holders. The way this issue was discovered in fact was some app developers found their rankings were dropping rapidly in what appeared to be abnormal manner.
Of course this incident brings up the point about the much ballyhoohed walled-garden that Apple maintains in order to protect its customers from viruses, porn and other security risks. It just goes to show you that even the most well-designed and thought out plan can be penetrated by malicious developers.
It is unclear however what damage there will be for iTunes customers if any as of course Apple is able to cancel purchases which are not authorized.
If you are a concerned iTunes App Store user a word of smart advice comes from David Murphy who says:
Be sure to look into your "previous purchases" listing from time to time for evidence of unauthorized activity--or just unlink your credit card details from your account!