If you ask Warren Buffet, he will have a very simple answer Greed and fear.
^ This.
Bitcoin Going UP = Greed = BUY BUY BUY
Bitcoin Going Down = Fear = "SELL SELL SELL"
On a sidenote take an appointment from dr.fontas he will tell you more about pumping/dumping.

The thing you are talking about is the after effect of change that happens. i.e. greed and fear only comes into effect when the curve either dips down or up. but what causes the curve to go up and down are many. Most of them being over supply or under supply.
this case can be better demonstrated with the recent drop in BTC. this drop happened because of a sudden supply of ASICS in the market, a small number of people got the ASIC's and started to mine. they earned a good number of BTC . however the BTC is useless to them unless they get services or fiat. this sudden rise in supply of BTC in the hands of a few increased supply. there for the prices started to drop because of a few who needed to offload the btc.
My prediction on the ASIC arms race is that this will only bring down prices. may be in another 3 months it will stabilize and go stable for another 2-4 years till Q-chips start's becoming viable to mass produce, well when that happens i guess things are just going to sky rocket.