Very few people understand and are not afraid to say where the value comes from. Bitcoin is a collectible. Network does not care how much 1 BTC is worth, the price is determined simply by the amount of people willing to hold a coin or two. Why they want to hold it? They believe there's enough or even increasing amount of other folks sharing the same belief. And if it holds true, then they get awesome payment network which gives them real purchasing power: to spend their money as they please when they want. So the value is essentially based on leap of faith or some sort of a bet. As time goes on and more people get serious about their belief, the stronger the reliability of BTC as a "store of wealth". Like with gold.

See also excellent article by Nick Szabo (who is a candidate for being Satoshi): http://szabo.best.vwh.net/shell.html