I'm not sure that opacity is necessary to the banking industry. Unless you think something like fractional reserve banking depends on opacity - which I don't. Under fractional reserve banking, there is more money listed in bank accounts than actual money (for certain meanings of actual money), but every moderately sophisticated participant knows what's going on. If you are financially sophisticated enough that you are bothered by fractional reserve banking, then you ought to agree the opacity isn't an accurate description. And if you aren't that sophisticated (bounded rationality and such), then fractional reserve banking is irrelevant to you.