Thus, PoE simply instantiated the model as the baseline of its currency. Every non-equippable item served dual-purpose, as both currency and consumable-utility.
However, their system isn't terribly sufficient, as trade comes far easier than it did in Diablo 2. Where D2 limits one to trade within a lobby of 8 players, or act outside of the core game, PoE has a /trade channel for the entire server. Their model, based on what I imagine was similar rarity rates as D2, falters under the greater population of a global marketplace, and rapid inflation incurs regardless.
However, PoE has a second system in its sleeve. The primary servers for playing are reset every 2 months.
So the economy is reset as well, and can thus survive
Also another interesting economy was WoW's, where they able to mitigate the effects of inflation in a similar manner as PoE. They simply wiped out the value of all items on the server with each expansion pack. However, I have not played or read about WoW enough to be aware if the community gives up on the gold-based economy
My main point is that you can't trust player-driven economies if the developers are following the 'standard' game design philosophies, as without careful consideration, it is quickly driven to ruin.