It is backed up by nothing, the value only depends on people's money, and that is all, if you buy bitcoin, your money will be added to the market capitalization of it, and the price will go up, and this is what makes bitcoin so high at the moment, because people are investing every time more, and a lot of people is being introduced in.
So if all people decide to sell, then the price will drop to $0, and this is how it works.
You just destroyed thread (why) and as far as i know it is not linked to real money (and we really need to find its maker ) ,basicly what BTC does that borrows money from all internet for what? Because it is made out of nothing if you know what i meant here (and plus you farm nothing then basicly thin air) when i think about it his maker is genius when you think deeper he made 0 to 4000 out of nothing. So if all people decide to sell, then the price will drop to $0, and this is how it works.
