People believe bitcoin is backed by nothing. I think that is not the truth. I believe bitcoin is actually backed by people themselves. It is backed by none other than just you. We all witnessed the price has been fluctuating by all those FUDs and bad news. The price changes by emotion and non logical facts. I believe you hold bitcoin no matter what happened and would happen, and believe it is backed by all of us, it would make a history. 
No currency is backed by anything, even if a currency was backed by gold you need to ask what backs that gold? And the answer to that is simple, nothing backs gold except the trust people have put in it for thousands of years, bitcoin is the same, we trust in it because it is an incredible concept which has been accurately described as digital gold with the huge advantages that brings.