FWIW, This w3.org web standard for per-fee-links (dated Aug 1999) describes a micropayment system that can be denominated in arbitrary currencies, giving "airli

FWIW, This w3.org web standard for per-fee-links (dated Aug 1999) describes a micropayment system that can be denominated in arbitrary currencies, giving "airline miles" as one possible example: https://www.w3.org/TR/WD-Micropayment-Markup/#Appendix%207 https://www.w3.org/TR/WD-Micropayment-Markup/#Appendix%207