Only currencies I'll accept are Earth Alliance credits or Centauri ducats!

Honestly, we haven't even got a burgeouning space tourism industry and some total dicks are already saying "and here's the currency the whole world will use in space."

Bollocks! When we do get motels, casinos and B&Bs on the LEO satelites/moon/Mars/asteroid belt t'll wind up like everywhere else - electronic transactions on your (RFID chipped) VISA/MasterCard/Diner's Club,

What currency is accepted is determined by those performing the transaction, not by some bunch of Earth-bound ninnies making a decision on behalf of everyone.

Which means if the Mare Imbrium B&B or the Olympus Mons Hilton are prepared to accept Euro, US dollars, Flanian Pobble-beads and ducats (Centauri or otherwise) as well as VISA, then that's what currencies are going to be used.