What I'm imagining is a currency that can't be hoarded or turned into a scarcity.
It would be designed to favor those who used their currency to purchase tangible items.
A single unit of currency (i.e. 1 AltCoin Dollar) would have to be spent within a certain time, or be forfeited. Where might this forfeited currency go? Perhaps it could be nullified and a new potential mining block be created.
The length of time one could "own" a certain unit of currency could be influenced by a number of factors if necessary.
The implications of a 10 year time limit would look much different than a limit of 7 days. Perhaps there is a sweet spot to this tweaking.
Obviously this would prevent people from just sitting on their wealth forever. It would encourage human interaction and spending of currency on tangible things, goods and services.
Has it been done and is it realistic?