i have a question about passwords. If you have a weak password your coins will be stolen, because of the rainbowtable guys. But isn't it true that when these rainbow guys try to bruteforce an account. And every time they enter a non-existing passwords then each time a new account is created within next?

So if you create a new account with a weak password you probably access an already created account which was bruteforced earlier. There are ofcourse no coins in these accounts so you think they are new. Is there no way to signal that you are entering an already existing account? So you know that you should not send coins to this 'new' account