Remember 2 days a go about iTunes account hacked that I posted, here is a response from Apple concerning that case. Apple had released the statement on the abnormal increase of the unpopular apps which dominating top 50 positions in the App Store for Books category over the weekend.

The apps that managed to sit on top in Books category are developed by a Vietnamese developer named Thuat Nguyen, the App developer is being removed now from App Store because of violating the developer terms. Furthemore, Apple recommends any users who had their credit card numbers or iTunes account comprised to immediately contact their financial institutions for chargebacks request, of course change their passwords too, here Apple’s response:
The developer Thuat Nguyen and his apps were removed from the App Store for violating the developer Program License Agreement, including fraudulent purchase patterns.
Developers do not receive any iTunes confidential customer data when an app is downloaded.
If your credit card or iTunes password is stolen and used on iTunes we recommend that you contact your financial institution and inquire about canceling the card and issuing a chargeback for any unauthorized transactions. We also recommend that you change your iTunes account password immediately. For more information on best practices for password security visit http://www.apple.com/support/itunes.