Google Wallet is a great idea - in theory. In practice? The service has been plagued with problems; slow adoption, a lack of NFC devices, the existence of ISIS generally, and a public image crisis after security concerns. The biggest problem, though, has been the decided unwillingness of carriers (except Sprint) to support it.
That's because everyone but Sprint is banking on Isis, which has over $100 million in financial backing from the likes of Verizon, AT&T, and T-Mobile.