According to TechCrunch, scammers are exploiting iTunes accounts linked to PayPal:

Reports are appearing this morning about a major security hole in iTunes accounts linked to PayPal. At least one group of scammers has found a way to charge thousands of dollars to iTunes accounts through PayPal. One targeted customer told us, “My account was charged over $4700. I called security at PayPal and was told a large number of iTunes store accounts were compromised.” His email was filled with nearly 50 receipts from PayPall for $99.99 each. He was able to catch it before his bank disbursed funds to PayPal.

TechCrunch: Fraudsters Drain PayPal Accounts Through iTunes

No details yet on how the accounts were compromised.