The ACH issue is why Donald Knuth no longer sends out his famous checks to people who find errors in his books but now uses mock check-like certificates. Typica

The ACH issue is why Donald Knuth no longer sends out his famous checks to people who find errors in his books but now uses mock check-like certificates. Typically people didn't cash the checks but put them on display for bragging rights, and apparently somebody used the numbers to scam his bank account.