http://support.google.com/wallet/bin/answer.py?hl=en&ans...
In regards to reward points- This article also mentions "Certain transactions may not earn your typical rewards or be eligible for certain benefits. Learn more about rewards. Please contact the seller with any questions about your order."
Most people seem to use their credit cards to pay for things instead of their debit cards to get reward points. This will definitely discourage people.
Er, actually, I think that's just for online purchases. Google Wallet in the past has used a Masterpaid prepaid card for NFC transactions and my understanding was that the recent update causes a more direct credit card emulation as it will allow to use any sort of VISA/whatever.
This has ramifications for rewards programs: http://support.google.com/wallet/bin/answer.py?hl=en&top...
It looks like they're going to give you the option of getting a physical representation of that proxy card.
One thing I'm curious about though is how chargebacks get handled with this system. Say I have the proxy card pointing at my Amex, I go buy something, and Google forwarded the charge to my Amex. Now for whatever reason I need to do a chargeback. Who do I talk to, Google, or Amex? How would that even work?