[Dixie Yooper]

Debit cards work through Visa or MasterCard. They do not have instant access to your checking account. Sometimes it can take several minutes for the transaction to complete from the retailer through Visa or MasterCard then to your bank. By then you could be out of the store and long gone only to find out your transaction bounced if you didn't have overdraft protection. In that case, the fees would be much, much worse, from not only your bank, but also Visa or MasterCard and maybe even the retailer's bank.

[SoothingDave]

All true. But the banks should then post any debits in the order that they occurred, not in the order that generates the most fees for them. It’s blatantly dishonest.