Google Wallet PIN security has been cracked. If your phone is not rooted then there is no worries, it only affects rooted phones. Peoples Google Wallet PIN is encrypted on their phones and recently a powerful method was found to expose the hex-encoded PIN information that is in the database.
Unfortunately this method was released to the public. On the bright side Google has been notified of the issue and they say they know how to fix it. Google will have to move your PIN information to be maintained by your bank. But be aware that this cause some changes to the terms of service. All in all just be aware of the security breach if you use Google Wallet and be careful.