Apple on Friday put a prominent notice on all the free-to-play games listed in the iTunes Store: "Offers In-App Purchases." The move follows Apple settling a lawsuit over some free-to-play games selling in-app purchases but not needing a password to spend money on them. There were also reports from Europe of children spending thousands of dollars in games without their parents knowing until they received their bill.
The warning is prominently displayed right under the game's icon. While free-to-play games already listed their top in-app purchases this is most likely a move by Apple to give it more protection from future lawsuits. While the warning is only on desktop version of iTunes, it is likely that it will move to the iOS version and web version soon.
With more and more games going the free-to-play route, these sorts of warnings are bound to become more and more common.