No evidence data has been compromised, Gabe Newell advises caution

Valve's Gabe Newell sent out a notification today warning patrons of the company's digital digtribution service Steam that hackers may have obtained a copy of a file containing payment transaction details dated 2004-2008.
"This backup file contained user names, email addresses, encrypted billing addresses and encrypted credit card information. It did not include Steam passwords," said Newell.

"We do not have any evidence that the encrypted credit card numbers or billing addresses have been compromised. However as I said in November it's a good idea to watch your credit card activity and statements. And of course keeping Steam Guard on is a good idea as well."
Newell said Valve are still investigating and working with local law enforcement. Some users may also recieve more formal notifications in accordance with state law.