Let me ask you a question. How do you get to know the value of a stock? Simple...Its value comes from the current and potential earnings of the Company. So how do Bitcoins get value? Bitcoins get value based on what you and other investors are willing to pay for them. Simply speaking....Its value is totally open to interpretation.
Bitcoins encourage speculation. They are not backed by anything. There's no Government or Central bank to regulate the supply of Bitcoins. You invest on hope that prices will go up, with no firm logic as to why you are investing. This is speculation which is very dangerous. You could lose all your money in seconds.