I've only made multi-item purchases from iTunes a few times, but every time I've gotten a call from my credit card company within a couple hours. The last time they said that it's become so common for fraudulent activity on a card to start with a "run on iTunes", then move on to other online sites if the card still works.
The only thing I would recommend to Scott Hansleman is to drop PayPal. They can be easier for small donations online, but with how far behind the curve they are in consumer fraud protection I refuse to make purchases with paypal anymore.
There's a difference between someone using your creditcard to buy stuff on iTunes with a different iTunes account* and someone using your iTunes account to buy apps. In your case I'm guessing they did the first thing.
* = possibly not their own; they might own the apps that you're buying or make money through affiliate networks. And of course they could buy gift cards with your cards and sell them on eBay through another payment account.
The only thing I would recommend to Scott Hansleman is to drop PayPal. They can be easier for small donations online, but with how far behind the curve they are in consumer fraud protection I refuse to make purchases with paypal anymore.