Bitcoin cannot crash nor go down against the dollar. You can print as much US dollars or fiat currency as you want. BUT YOU CANT CREATE MORE THAN 21 MILLION BITCOINS. If everyone just realize that fact, it would never stop going up. It seems like the idiot stupid fools that are selling since December don't know that. It is just as simple as that.
Those selling are just afraid that they are going to lose all the money that they spent investing into bitcoins, they have no foreknowledge about it's potential, they were just in to make some profits and that's all.