I currently work on a client accounting system at a large bank, and have worked at another large bank previously. While what you described may happen somewhere

I currently work on a client accounting system at a large bank, and have worked at another large bank previously. While what you described may happen somewhere, the pattern in banking systems that I've seen is pretty straightforward and simple to reason about: a cash flow produces two ledger entries within a transaction and is committed with no concept of distributed rollback. If there are problems with some sort of subsequent step (e.g. the actual dispensing of cash in ATM or invalid routing instructions in a cross-border payment), the original cash flow is reversed with a reversal of the original two ledger entries -- which is precisely what Ayende saw on his statement. If a correction is also required in addition to the reversal (perhaps SOME of money was dispensed before an ATM loses power), the correction will be encapsulated with another pair of ledger entries. (These various cash flows will then typically be placed on a payment bus for further processing by various other systems that perform recon, liquidity management, etc. Again, there is no distributed transaction, just simple double-entry accounting and straightforward transactional message queues.)