Coruscation

A theory of Aaron Fine, a partner and consumer banking specialist with the consulting firm Oliver Wyman. He argues that more affluent customers have suddenly become a lot more valuable to the banks.

Why? Well, a big chunk of the fee income from the more stretched classes of bank customers stands to go away because many of those people will opt out of paying fees to overspend.

"I expect you'll see another wave of innovation coming from the banks," he said. "And perhaps the first segment they'll address is the higher balance accounts."