What could be the reason for the price of btc to go down?
Supply and demand, buddy.
There is a pretty static amount of bitcoin being produced at any given time. The more people are buying it, the more expensive it is.
The less people are buying it, or the more people are selling it (so the exchanges have more), then the price goes down.
i think we all know that part .... i think what he/she is asking is why the sell off. why arepeople jumpng ship. it takes hundreds of thousands of coins to go from 150 to 100. thats about ten million dollars gone. probably they see the down slyde and so they will sell and buy back in at a lower price.... this is a positive feed back loop. but what will brake it is about twenty people is all to all put in buy orders at once with about 10 coins each at a price about 5 above the current market value. this will cause the shift and then people will think oh here is the bounce and all start to buy and bam you got yourself a panic buy and a huge rally. its just the opposit of the bubble but instead of a pop and it falling it like a boom and rockets up.