We see the biggest risk to Bitcoin being its substitution and/or parallel use by other crypto currencies. Bitcoin die-hard fans claim that this is never going to be an issue since Bitcoin was the pioneer and as such enjoys first-mover privilege. This argument is probably flawed because although the BTC is used for payments, this is only a relatively small % of all Bitcoins. One of its primary uses is being a store of value and for this reason other crypto currencies can always step in and enjoy similar status if aggregate demand requires it.