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 .
There's many reason why they dump their bitcoin either they need money immediately, they not know how to hold so they sell it and panicking because when they see the market down they panic immediately and sell it all. If you are really know about cryptocurrencies and know how hold it I think you will not sump you bitcoin. Some of us is tired to read and learn more about cryptocurrencies that's why they end to always dumping if their bitcoins.
I think one of the biggest factor is panic because bitcoin is easy to move because of rumors, so many people easily panic. yeah we can see some examples, when many negative rumors about bitcoin, prices will go down and vice versa when a lot of positive news, bitcoin prices will rise.