Last week, there were issues reported with Google Wallet vulnerabilities with the ability of thieves to use prepaid credits in Google Wallet.
Google has temporarily disabled prepaid cards in Google Wallet until they find a fix.
Google posted in the Google Commerce blog that Google Wallet is secure because it is protected by a PIN. They note that rooted Android devices turn off the lock feature in order to get to the root of software features.
"we temporarily disabled provisioning of prepaid cards. We took this step as a precaution until we issue a permanent fix soon...In the meantime, you can be confident that the digital wallet you carry provides defenses that plastic and leather simply don’t"
If you are using Google Wallet, you should lock the screen with a pattern or pin.