In the last '90s I worked as System Operator for a company which sent several thousand automated account renewals to credit card companies each month. We had been sending 9-track tapes via Fed Ex, and I was tasked with converting all these to digital transfers. We ended up with a mish-mash of different methods, dialup modem, encrypted email attachments, etc. but American Express had a rather unique approach.
They had us FTP an unencrypted, unzipped text file to a folder with our account number on their ftp site. Logged in as anonymous. With full access to all the other folders showing all their other customers' data transfers. They didn't clean up the folders either, so some of the other customers had a year's-worth of data transfers piled up. We couldn't believe it.