The original plan for currency was the use of dollars that would come with each player account and could be found scavenging.
The 'evolution' of currency was to add several types of objects such as bottlecaps, buttons, beer tabs, etc. that could be stacked in large amounts in a player's pocket slots.
Tribes could then assign one of these as an official currency for their tribe, but it wouldn't be as complex as creating Shinra coins or 'Shrimps'.
Tribes could also assign exchange rates.
Right now, after discussing with players and reading threads such as this one, we might stick with bartering at the beginning, and later add the tools for tribes to designated currencies if they wish to do so, as mentioned above.
We'll soon see once the tribe totems are in and players start trading more.