In your opinion what are the reasons that let someone start dumping his bitcoins and walk away ?
I personally (and this is just my opinion) that it's more panic then simply his need of money or something else , as we saw on the BitcoinXT last time , people started to panic and simply sold their bitcoins and that caused a drop in the price .
It could also be a manipulation strategy also. Some groups of people initiate dump to create panic and when the price dumps big investors take it to their advantage to buy in huge amount to earn huge profit. However, it is reality also that people dump coins due to immediate need of money or some just lose interest and would wanna invest in something else.