In the first place, the price of Bitcoin is volatile thats why we cannot predict the price if it goes down or rises. But one thing we know is that, unless there are investors and investments in Bitcoin, it will stay on track. Investors are also one of the main reasons why there are ups and downs. When investors sell their assets and others follow when there is a dump and vice versa
Because there are no indicators that can predict the number of people who sell a lot of coins all at once. There was no indicator that showed mt.gox will be hacked, there was no indicator that said bitcoin is going to 20 thousand dollars, there was no indicator when china banned bitcoin, there was no indicator that Craig would sell a lot of bitcoin at once in order to fuel his satoshis vision coin.
These are all "out of nowhere" stuff that affected bitcoin price that we couldn't ever known beforehand. All these people who keep on trying to do predictions about bitcoin price are probably new people or people that want to look cool or something. No one in the whole world could know the price a minute from now because some crazy stuff could happen and we would all watch it in awe.