There are lots of reasons why the market value of bitcoins is going down. One of these are the external factors such as political policies like new laws and agreement.
Another thing is the demand in their services which slowly decreasing the market value when the demand falls down.
Many reasons may be founders of a joint venture, or perhaps operational costs are too high, or prohibited by the local government, and so on. One thing you need to pay attention to, although at this time perhaps Bitcoin's price drops because of overbought or may be supported for other reasons, but it will not last forever. Later, the price of balance can continue to rise, until the overbought price level continues to rise.