I placed a buy bet on bitcoins with Spreadex today.The round turn spread is about 5%,and the annualised cost of running the position is just over 5% [LIBOR plus 5%].The margin is 50% of the value of the contract.
It is a lot simpler than actually buying bitcoins from ,say Mt GOX,and finding some safe way of storing them.
PLUS 500 also seem to be offering spread betting on Bitcoins.Their spread is narrower,but their annualised cost of running a position seems to be higher.IG offer some binary specials,but they look unattractive.
@quincunx - what I find a little daunting about trading Bitcoins on SpreadEx for instance is that the market is VERY volatile. The value of Bitcoins can triple in a day etc. I guess you can make huge profits potentially. Where do they get the value of Bitcoins from? As far as I am aware, it is not listed like shares would be on the LSE or AIM etc.
Spreadex told me that they currently get the value of Bitcoins from Mt Gox - who are currently the largest Bitcoin Trader.I did ask them what would happen if Mt Gox stopped trading Bitcoins,and they told me they would then get their prices from another large trader or traders.