The problem you run into is finding a trusted, centralized authority who would back the coin by gold - fail because you lose decentralization. Having individuals back it leaves you with no guarantee they will perform. At least with the current system, bitcoin has its own value based upon its unique features, qualities and benefits. These features, qualities and benefits are valued enough by people like me who will sell you their gold for your bitcoin.
Trader Steve
http://www.GoldStarBullion.comGoldcoins would also have value based on the unique features, qualities and benefits of bitcoins because the hypothetical Goldcoin was designed to deliberately have those same features. Goldcoins would likely trade at values above their redeemable gold value. Goldcoins would just have an additional feature because goldcoins would be backed by gold.
The main criticism I am hearing about the Goldcoin concept is that the gold backing may fail. To me this is an admission that it would be good if the backing did not fail which means people have an intuitive sense that it is better to have backing than to not have backing. If the backing of goldcoins described above were somehow magically guaranteed, then would you prefer 10 goldcoins over 1 bitcoin?