It's fascinating to watch this, largely because Bitcoin has no "natural" value. The only utility it has is as a transfer of value from one place to another, and it can do that equally well with a bitcoin being worth $1 or $200.<p>But it's really interesting to watch the value ratchet up, and easy to see how you can do this - if people will only ever sell a bitcoin for (say) 1% more than they bought it for, and people buying things with bitcoins don't care if the things they're buying with it are priced 1% higher than they might, theoretically have been, then the price of bitcoins can keep increasing indefinitely.<p>Until, that is, some people decide that they want to get rid of a lot of bitcoins, and thus are willing to accept less than that, to shift them quickly. Then the price drops. And then more people might also decide to sell, so as to convert the bitcoins they have at the value they're now worth.<p>It's classic sentiment pricing - but without any of the value "stickiness" that you get when there's some utility to be gained from the objects you're trading.<p>(I'm not trying to talk Bitcoin down here, I find the whole thing fascinating. Just thinking out loud.)