Using a name system like this (microguy@goldcoin) would probably require a centralized database of names and addresses. This would avoid duplication of names, but also associate the name with the correct address. This system would not be trustless. A hacker could get into the database and change all the addresses to his own address. This is not a secure method.
A second means of doing it would be something like what namecoin does, in that it uses the blockchain to store the name data. This could be used to associate the name with the address and avoid having multiple addresses with the same name. Light wallets such as the GoldCoin app wouldn't have access to this data and would not able to use it. Nevertheless, this method is as secure as the rest of the blockchain is.