Re: The cost in kW
"And how is that any different to Barclays seeing and notarising all my transactions, as at present?"
I can't believe you're really asking that, but let's do a few comparisons:
Banks/money in government-issued and controlled currency: Strict regulations on what they're allowed to do with money. Not perfect regulations, and not always obeyed.
Facebook/money Facebook makes: Almost no regulations save for data protection (data protection regulations offer valid in EU countries and U.K. only). Facebook has a terrible record obeying even that.
Banks: They are not permitted to sell personal transaction history to anyone.
Facebook: They not only are allowed and are definitely going to sell transaction data to someone, but they already know the people they're selling it to and have customers eagerly waiting for it.
Banks: In most places, value is insured against a bank collapse.
Banks: Multiple available. Should it turn out your bank has not been sufficiently protective, you can choose a different flavor of not that great, but at least competition exists and is enforced.
Banks: Should you want to prevent them from knowing what transactions you do, you have the option to make a large withdrawal in physical cash and then spend the cash (offer only functions on some transactions, notably smaller ones).
Facebook: If you think getting a different currency out of their system without a lot of paperwork and paying quite a lot in fees is going to happen, you might not have read their documentation.
Banks: They are owned by many different people, and those people are interested in the profit of the company. So they aren't super happy to incur massive fines or lose all their customers and will change policies to try to prevent that.
Facebook: They are controlled by one person and he is already a billionaire. He doesn't need any more money and he will do whatever he pleases.
Government-issued currency: Supported by the government of the country. As history shows us, this is no guarantee that it will definitely retain its value, but it is somewhat likely to do so if the country is run democratically and has a large-enough economy.
Facebook: They can pretty much decide at any time to reduce the value of their currency and have fun trying to stop them.
Government-issued currency: The government of your country of residence has the ability to ensure this currency can be used to pay people; sellers can increase prices but must accept payment.
Facebook: Should Facebook stab sellers in the back with high fees, sellers would be completely in their rights to stop accepting it abruptly. This makes Facebook's currency less reliable.
Nobody is saying banks are great. We can all get together later and compete to complain the loudest about banks, and we have plenty about which to complain. But that doesn't stop Facebook from being worse.