Last night I had a delicious dinner at Momofuku Má Pêche with a friend who was in town from Germany. When we were paying my American Express card was declined. That is certainly not the end of the world but is annoying and in different circumstances potentially embarrassing. So this morning I called American Express to find out what was going on and was told that I had an overdue balance on a *different* card. Now (1) that card hasn’t been in use for years and (2) the balance is *trivial* compared to my main American Express card on which, among other things, I book all of our family vacations.

I can just imagine what was going on behind the scenes. Someone came up with the idea of figuring out how to tie information on different cards together and then block an active card as a way of collecting a balance on an inactive one. So far not an entirely bad idea. But here is how this went off the rails in a big way. First, there was clearly no check to compare the size of the balance to the size of the activity. Second, there was no attempt to contact me before blocking my active card, even though American Express has both my email address and my cell phone number.

It would not have taken a lot of thought to contemplate both of these and using Twilio it would have been trivial to implement an SMS notification. So the lesson here is: before you run an algorithm like this think through the resulting customer experience. It is all too easy to do a lot more harm than good.