I'm passing along a story a friend shared with me. This is totally and completely second hand, and I make no claims to the accuracy of the story. That said, I still find this interesting.

Several years ago, a friend of mine was on a Delta flight and she was seated next to the former (retired?) VP of Marketing for Delta. This was the VP who was responsibility for the formation of the frequent flyer program.

Did you ever wonder why your SkyMiles number is a ten digit number? It seems that they were in such a rush to get the program to market that they didn't have time to wait for Delta IT to write the code to manage the program. So they used whatever data field wasn't being used, and the one they found was ten characters wide, just like your SkyMiles number today. That field was the telephone number.