I tried to just restate my previous comment but it seems I wasn't clear enough. Okay, once more. Account should be understood as user account, not bank account.

I tried to just restate my previous comment but it seems I wasn't clear enough. Okay, once more. Account should be understood as user account, not bank account. Forget about Bitcoin for the moment. We build a new distributed currency. You can sign up for an account and with that account you get one vote to vote for (blocks of) transactions you consider valid. But because there is no central authority performing identity checks the bad guys can just create a million accounts and use them to vote for bad (blocks of) transactions. This is what I previously called fake accounts - several accounts by one person to vote for bad (blocks of) transactions. And now back to Bitcoin. Bitcoin's solution to this problem is mining. A vote in the Bitcoin network is a mined block and because mining is expensive this prevents users from casting arbitrarily many votes which is the logical equivalent of a fake account prevention mechanism. It is not perfect because with enough money for hardware and electricity you can still obtain more votes than others but it is no longer as easy as signing up for a million accounts with a million different email addresses. I hope this helps clarifying my point.