I just booked two tickets on Eurostar (the channel tunnel train) for a trip from Brussels to London later in the month. My booking confirmation contained the following warning:

Collecting tickets from a French Station
If you wish to collect your Eurostar ticket(s) from the Automatic Ticket Machines / APV at a French station, please note the following conditions:
A French credit or debit card must be used for payment.
American Express credit cards cannot be used for payment.
Payment must be made in Euros (€).
The total value of the tickets purchased does not exceed 800 Euros (€800).

Sacre bleu!