I'll say it. For the bitcoin has built in link between the price and the downward pressure on the price.
Currently, ($115) miners create around $400.000 daily in new bitcoin, and when the ASIC sellers get their production in order, a large percentage of that money will be sold on the exchanges every day. This means that you would need $200k to $300k every day, just to prop up the bitcoin price.
That's about double what Bitpay, the largest processor does each day.
So, for each $1 in Bitpay volume (not profit), you need $2 to $3 in "sucker" money. Sure, the price will come down.
Bitcoin players are mostly middle class IT people, they don't have an urgent need to cash out
Suppose that most people have a motivation to cash out after 100-1000x price appreciation (a historical scale for 2011 price bubble), before that, there won't be any major sell off
If more and more new adopters enter the game, and each of them waiting for a 1000x price appreciation, there will never be a crash unless the available USD is not enough
FED is going to tighten sooner or later, that will generate some downward pressure due to reduced USD supply, but that's still 1-2 years away
Like NGZhang said, valuation is about trust. Currently bitcoin has not reached a deserved value because people are still doubt about it, but more and more people are starting to lose their trust of fiat money, sooner or later they will realize that it is better to trust mathematics and networks instead of a bunch of politicians and bankers
