Apple Makes Changes to Prevent Kids from Accidental In-App Buys
The new version of iOS adds another layer of security: in the past, in the first 15 minutes after an app was purchased, you didn't need to enter the iTunes password again. Parents who bought a game might hand the device over to a child, only to see a huge bill later as the children didn't understand they were racking up a bill.
However, it doesn't mean that a password needs to be entered for every in-app purchase. Once "unlocked," the in-app purchase policy means that purchases can be made for 15 minutes after the password is entered. Parents need to be remember that, and not just hand the device over.