Well whilst its unlikely that traditional money will completely disappear any time soon, the notion of paying for most things just using plastic might have come a lot closer with the introduction of Square - an iPhone credit card payment system that's the brainchild of Twitters Jack Dorsey.
Currently in public beta, Square (watch the video) is a nifty little iPhone add-on that lets anyone with an iPhone accept payments from a credit card. Basically, its the combination of an iPhone app and a small card-reader. Any individual can use the devices - you don't have to be a registered company or anything. All you need is the app, the dongle and an account. So if you say, owe me $1000 (which would be nice for me) all you would need to do is swipe your card into my iPhone and wed be square, if you pardon the pun. Once customers have swiped or keyed in their credit card numbers, the phone allows them to write their signature using the touch screen to verify the purchase. What will an iPhone do next?