There are billboards popping up in my area that show a bitcoin logo and say "The revolution has started. Where do you stand?" Where I'm standing is, at a good safe distance from the sign by the cliff that says "watch for falling currencies".
Krugman was right: bitcoin has solved the transactional part of a digital currency, but not the value part. Any value it holds is entirely speculative, with nothing underlying it.
Buying bitcoins is like buying stock in a hot company with no assets or revenue. It's like buying bonds from a popular issuer who never promised repayment. It's like buying commodity shares in neutrinos.
It looks good now because its designed-in scarcity makes it naturally tend to rise in price as people buy in. Considered as a currency, it has built-in deflation (which, by the way, would make it a terrible idea to use it as an economy's primary money). So as soon as anyone pays real money for it, it immediately becomes a bubble. But because of the lack of a base of real value, when this bubble pops, there's nothing to stop the price falling all the way to zero.