Asked if Google represented a threat to banks, Joseph DiVanna, managing director of consultant Maris Strategies, didn't offer much in the way of comfort. "If you think about the footprint that Google has, it's big," he said. "It's the same kind of footprint that we had in retail [banking] years ago with branches. I think Google is a force to be reckoned with."

The company's Google Checkout payment service already places it in competition with pseudo-banking operations such as eBay's PayPal. A Google-branded bank might be particularly appealing to younger consumers, whose expectations of financial services have been shaped by easy access to Internet-based services.

"We're seeing the very early stages of a fundamental shift in how people are banking and commissioning transactions in the world itself, and Google is catering to that group of people who are going to inherit the next wave of wealth." Maris said. The ability to draw together data from disparate sources would also be important: "Customers want to aggregate many [financial] relationships together."