If we had a magic wand, and there were no technical, business, or security constraints, what would the ideal micropayment system look like? A button on the web page that, when I press it, sends $0.25 from my bank account to the web site. Isn't something like that the holy grail? No need to "have an account" at the web site, and "have an account" with the payment processor or pre-load things with funds or any of that garbage. I already have a bank account, why do I need a handful of other accounts all over the place?
There's the UX. I think it would be successful. But nobody has managed to build it yet.