You also need a central point for it (the backer).
So to have an asset-backed and at the same time truely decentralized coin is not possible. Or is it?
Unobtanium might be a coin that in the future is backed by metal in a decentralized way. Many investors (each for themselves and privately) could start trading for metal and/or putting out other backing-ideas.
So Unobtanium could be backed with silver by myself and others too in the future.
It's still the future though.
Personally I believe the reason Bitcoin hasn't taken off properly is because it has no backing. Why is it worth $500? Why does it swing from $300 to $600. Because people do not have faith in its price. Backing brings with it stability because people know that the value of the cryptocurrency can never reach $0. Bitcoin cannot boast that. Yes, Bitcoin is a technologically genius, but in the real world people want backing. Which is why we have banks. I like having someone who can reverse payments if I make a mistake. So yes I agree this is not a decentralised coin. Its sort of half and half. I think crypto is the future don't get me wrong, however I believe that to establish itself, and to gain trust from the world it needs a backing of some sort. People are to weary of it to start investing large amounts of their money into it. In the past it has been precious metals which have successfully done this.
PS. Apparently you can ship the Silver bullion. Read it in the FAQ.