"Globally, multi-banking is increasing as customers search more actively for the best rates and products," the E&Y report says.
Others are even flirting with alternative financial lifestyles outside the strict banking norms.
"Customers remain wary of non-financial providers, but banks face a potential threat from new entrants offering better rates, more personalised service, stronger technology or more attractive rewards," E&Y says.
And with all this alluring financial promiscuity on display, consumers are seeking information they can trust about the best performers - mostly from family and friends "but online reviews and opinions are also gaining influence".
According to the E&Y report, customers are more likely to use financial comparison websites than ask a reputed adviser about banking.
"Comparison sites have achieved success across regions as diverse as Western Europe,
Latin America and Asia-Pacific, although they are slightly less popular in some mature markets - most notably the US, Canada and Australia," the study says.
"Globally, it is remarkable that comparison sites are now seen as playing a more important role than financial advisors, although that is not yet true in markets such as the US and Canada."
Despite all these threats to financial fidelity, however, the vast majority of customers don't want to leave home just yet.
"Overall, 87 per cent of global customers are either satisfied (68 per cent) or very satisfied (19 per cent) with their main bank," the E&Y report says, proving, perhaps, that in finance most of us just want someone dull we can trust.