For those who haven't noticed, a single bitcoin is worth almost 47 dollars now, over 30% more than two days ago:
http://bitcoincharts.com/charts/mtgoxUSD#rg5ztgSzm1g10zm2g25...
this is not a market for weak hands.
Global GDP futures perhaps? It would be interesting to have a currency worth a particular percent of global output.
It appeals to libertarians for this reason. Doesn't appeal to me because I like stability in my currency and am happy to have central authorities that try to ensure that, but it appeals to libertarians.