If this happens to you immediately change your password and remove your credit card information from the iTunes site/app. You do this by:
- Clicking on the store menu while in iTunes and then selecting the "View my account" menu item. From there click "Edit" on the main screen where it says "Payment Information" and select credit card type "None".
- Next change your password. In the same "View My Account" screen click "Edit Account Info." That will take you to a screen where you can change your password.
Ok, now that you've protected yourself you need to get your money back. Unlike Amazon or Zappos contacting support and reporting the fraud DOES NOT lead to a refund. They will direct you to your credit card company to refute the charge. I did this and it appears to be successful (I found it disappointing that Apple didn't just take care of this for me).
As a side note, when shopping online make sure you have a credit card company that takes responsibility for stuff. Amex has always been great and I'm sure other good companies exist as well.
Looks like I'm not alone here. This blog reads like I could have written it.