[reissbaker]

What were the non-hardware non-card payment methods attempted? I'm familiar with NFC, and somewhat intimately familiar with Square and its card-based rivals, but the only alternatives I know of are those pay-through-your-carrier attempts that are an even bigger can of worms than a card company. Were there others?

To reference your Visa point (which I suspect wasn't serious), Square was card-based long before the Visa investment.

[thinkcomp]

Starbucks (for payments) and the airlines (for boarding passes) have done pretty well with barcode scanners. It requires hardware only on the merchant side than most merchants already have in one form or another.

[reissbaker]

Er. But unless you've given Starbucks direct access to your bank account, those are fundamentally card-based too.

[thinkcomp]

Not quite. Starbucks uses its own pre-paid system that does use a plastic card, but one without any major network's logo on it. It's just store credit.

[vidarh]

So worse than both cash and cards - suddenly you have to have small balances sitting on multiple proprietary cards. No thanks.

[corin_]

And in America (I believe - last I heard it was rolled out in some American cities but not others, nothing here in the UK) the iPhone/Android/Blackberry(?) apps let you manage your account balance, and you hold up your phone for the cashier to scan the barcode off your screen.