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. 
When we talk about something being backed up, we mean those that are behind and sponsoring that particular project, investing funds in it to make sure that it continues. Currencies cant be back by a particular organization or whatever it is they think, rather it is being backed by individuals. And for Bitcoin, we are the ones that are backing it up. So Bitcoin is fully backed up, and by us. Anyone telling you that Bitcoin is not backed up is a pretty good liar.