@johnser, what investment banks are involved? Google are doing this with Barclaycard and Comenity Capital Bank, neither of which is an investment bank. In fact, issuing credit cards (or selling mortgages to the public) is not (by definition) investment banking.
Furthermore, the UK credit card is issued by Barclaycard: Google is only providing branding and marketing.
People already pay for Adwords with a credit card. All this means is that you can now pay with a Barclaycard issued card with a Google logo on it that can only be used to pay for Adwords. Barclays gets some new credit card customers, Google gets customers who have a credit card that can only be used on Adwords so they can spend more on adwords than on elsewhere.