Well, actually money per se are used mostly for gambling. The total daily turnover in speculative financial products is much much much (about one "much" for each order of magnitude) bigger then the daily turnover of all physical goods and services traded.
What stops governments and central banks from flooding economy with new (fiat) money? The new amount of money leads to inflation on all goods that are traded in that currency. (this is a bit different for the global currency - dollar, because its inflationary effect spills all over the world, slightly) This usually means increasing prices of local goods and depreciation of domestic savings. And this leads to voters' anger which can overthrow the government. This is the negative feedback in the loop which acts as a brake.
But there is no such a feedback in the world of digital currencies. The creators (often anonymous) do not need to fear voters' anger. They are not responsible for anything. They just create a currency, do some internet hype for it and hope that some of the speculative demand will move from existing digital currencies (which may now seem as overpriced) to the new one (which seems underprices considering its speculative potential). The creators are the first owners of the digital currency, therefore that can make a really big money if they succeed. For this reason the digital currencies will IMO never have any stable value…
Currently there already are many digital currencies traded on several exchanges. Bitcoin in not the only one, it is just the best known one.