You seem adamant about something that you clearly do not understand.<p>&gt;  Because if somebody can spend $1mln to perform 51% attack and move around $1bln, that will likely be done.<p>Then why hasn&#x27;t it been done? The answer is that bitcoin doesn&#x27;t even remotely work like this. You would have to sign a transaction, then double spend it to yourself, then BY CHANCE mine enough blocks to satisfy the person giving you whatever you are buying before they see the double spend.<p>That is not going to happen.  Someone receiving a million dollars will not give over a briefcase of cash the second they see the transaction, and that&#x27;s the only way something like this would work.  If you are taking money out of an exchange, the exchange would never even credit your account, let alone send you money.  They would see the double spend transaction and if by some chance (0.015625%) you managed to mine the next 6 blocks or so, they would just wait longer since there is a double spend out there.  By the time they might actually send you money, the chances of you mining all the blocks up until that time is practically zero.  So you would then be gambling your million dollars against enormous odds.<p>You might not want to believe that bitcoin works, and it might seem counter intuitive that the proof of work is important and useful, but this isn&#x27;t about how you wish the world works, it is about how the world ACTUALLY works, and that is why bitcoin actually works.