So this is once again an issue with cheques. :-DExample: someone steals your checkbook, writes a check to him/herself, and deposits it. A day later, you realize the checkbook is missing and notify your bank. The bank closes the account and gives you a new one. If ACH was instant, that money would be gone forever. Because ACH is not instant, you and your bank have time to prevent any damage from being done. The same applies to debit card transactions.
Debit card has multiple security measures: PIN, SMS password, transaction limit.
In EU your liability for use of stolen card (or another electronic payment device) is limited to 150 EUR (50 EUR for contactless operations). Of course this is for the period before you report you lost the card.
You can also get insurance that will cover these 150 EUR. This is an awful bad idea, but banks usually force you to buy it anyway. It costs around 0.5 EUR/month in Poland.
But this will only be possible to check from inside your bank and by a limited group of employees. It's exactly the same today.Which are the same numbers the bank requires to access your account. Even if the account number is hidden behind a separate ID, that ID can be used to find all transactions someone made and figure out who they are. A public ledger is not an option. There can't be more transparency than the existing system.
Null value? :-/It has to have null value.
You're still looking at this from perspective of mining bitcoin. This is a totally different thing. This will be an inter-bank transaction unit. No mining, no speculation, no variability in value.
http://www.coindesk.com/goldman-sachs-leaves-r3cev/The link speaks loudly enough...
Goldman Sachs was one of the first to join the consortium and one of the biggest banks in the USA. Pretty indicative it isn't a platform they're going to use.
"According to The Wall Street Journal, the bank has left the group, but notably intends to continue developing blockchain projects on its own. (Goldman Sachs is an investor in blockchain technology startups Circle and Digital Asset Holdings)."
I think you really don't get the concept. And you clearly have a huge fondness for cheques and ACH. Let's end this here - the dialog is getting boring by now.