A currency can't be decentralized and fiat.
I want to challenge this widespread belief.
In fact, some experimental currencies trying to merge the advantages of "decentralized" cryptocurrencies and "fiat-like" structures (e.g. with some kind of flexible emission structure, where a supply change is possible if the users agree, or with methods from barter clubs or time banks) do exist.
Of course there are challenges from them, the most important one is the governance structure. So these currencies don't work like Bitcoin where everybody has the same "rights", there are organizations (like mutual associations) which have the right to create new units, but these organizations are decentralized and democratic and everybody can participate.
Most of these currencies are based on an evolution of the "barter club" concept. For example, in Argentina there is
Moneda Par. It is a blockchain-based "mutual credit system", but also a kind of cash is possible it seems. It is created when people offer new services or products in the network, so it's based on the "economic growth" of this network.
I think Faircoin is also based on similar concepts. I however don't know if they are still active (their website doesn't work properly). As far as I remember Faircoin was in principle a decentralized cryptocurrency, but the association managing it could decide to peg it to a certain rate to the US dollar or other currencies, and to change the peg if the supply/demand situation changed.
