What I meant is that if you have a lot of things scheduled to be withdrawn from your bank account, and some sort of fraud or double charging happens, chaos ensues (as above.)
If you had a bunch of things timed to be taken from a charge account, and you exceeded your credit limit because some sort of fraud or double charging happens, identical chaos would ensue.
edit: and there's certainly not a vast difference in carrying $20K of credit and $20K in cash. We live in a world of negative interest rates.
Negative interest rates are a non issue if you have any debt, just pay down your house etc faster.
The problem is errors are random so your 'solution' is to keep huge amounts of cash in your checking account to deal with random error.
But, if I max a CC I would still have the cash in my checking account to pay other bills. If I don't have a CC and my checking account is empty I am going to have issues paying rent etc.
PS: Think of a CC as a financial firewall. You still need the cash to pay your bills, but keeping a redundant CC with an unused 15k credit limit is cheap.
