Speaking at Money20/20, Visa president Ryan McInerney admitted that historically the network has built a "big wall" and "moat" around itself. But all that is changing with APIs and SDKs opening things up for developers to build on.

This, says McInerney is "where the magic can happen" in commerce, helping to bring personalisation back to consumers by tapping into the power of the world's 10 billion connected devices, which hold huge troves of data about us.

The Visa boss used the example of his grandfather's relationship with the butcher who knew what he'd buy, had it ready to be picked up and would put it on a tab. That type of relationship may have been lost but is now returning thanks to mobile phones and applications such as Square.

McInerney insists that Visa is eager to work with partners, tearing down its walls, to bring this kind of personalisation to consumers.

Meanwhile, Citi's CEO of US consumer and commercial banking, Jane Fraser, also used Money20/20 to admit that the bank has traditionally been too closed off and too used to being in control. But like Visa, she says that it is now "learning that we don't have to build everything ourselves".

Fraser cited Citi's recent Latin American-focused 'Mobile Challenge' which drew hundreds of developers and "probably saved us a few years". The bank is now following up with a second challenge, which has attracted more than 700 submissions. She says that this approach is a huge departure for Citi but makes sense, enabling it to focus on what it is best at while drawing on a large pool of outside talent.