Following the discovery of two security exploits within Google Wallet, the Vice President of Google Wallet and Payments, Osama Bedier, released a statement reassuring readers that Google takes "concrete actions" to protect its users. The statement further indicated that, in response to Wallet's security scare, Google has put prepaid card provisioning on hold, at least until a permanent fix is issued (which should happen "soon").
Update 2/14/12: Prepaid card provisioning has been restored:
Yesterday afternoon, we restored the ability to issue new prepaid cards to the Wallet. In addition, we issued a fix that prevents an existing prepaid card from being re-provisioned to another user.
Read More