Gold has historically functioned as a settlement device amongst the various currencies around the world. Gold is stored at the Federal Reserve with forklifts moving pallets between various countries' deposits. That is expensive and difficult to audit. Gold also has dollar-settled derivatives that are used to manipulate its price. Bitcoin solves these problems from a central banking reserve and settlement vehicle's perspective.
Sadly, currently all Exchanges hold your coins if you want to trade. You should never keep your coins on such an exchange unless you are a Trader/Market-maker. So best practice is to move your coins to your own wallet as soon as possible. There are developments to implement full decentralized Exchanges, in which case you can keep your coins in your own Wallets.
thanks....thought it might have been such but never really knew. Given its instability etc as a new technology with no real backing (much like MFgolbal ha! *) i am surprised that there seemed to be a lot of people who had blind faith in Mt Gox, given the chatter about it. This was by people who were 'investors' and not traders. (* I got Corzined by MFG, 80%+ returned - but I had learnt from 08, and only had a 5th of what I might have normally had before then. ....but as we know no where is safe, but sometimes you are stuck having to deal with some m....f. )