Very good question. It seems obvious but actually, it is very important to understand this. Even real money that we use every day is not totally backed up. Countries can have their own money if they have a certain quantity of gold. Money is backed up by gold. Unfortunately, even the dollar is not strong enough when it comes to real money. Remember the subprime crisis? It has everything to do with virtual money and real money. Nowadays, recognition of bitcoin is hard. With time, more and more companies will use virtual money and maybe then we will not need any real money to back it up. It can work on it own.