Well, some people say that GLD will increase the Gold price "artificially" since it is letting more people participate easily.
I am not worried about every share being covered with gold bullions, since I don't expect many people to actually turn their shares into real gold and letting them deliver it. That is also why I would trade GLD instead of actually buying Gold. I don't have to take care of securing the metal. Anyway, I read somewhere, that they will sell or buy additional bullions depending on the demand for the ETF. So I guess everything is covered somehow.
I might actually look into their prospectus.
I am not so interested in Gold as an investment. It's more of a hedge or arbitrage play...
s.