Not sure which side of the fence I'm coming down on in your book. But I both run a business and like my amex card and the service I receive.

I also doubt that amex is being arbitrary. I'd stake a lot of money on their decisions being based on very sophisticated modeling. And even if they extended too much credit to somebody, and that could be seen as Amex' fault, they still should curtail the situation when they discover it. We can argue till we're blue in the face over whether they calculate risk right, but I bet they are better at it than me, simply because of the volume they process. Remember that the risk of somebody defaulting is different than a certainty. It doesn't mean you will, only that there is a chance you will. It is esitmated as a percentage, with confidence intervals. Right now Amex (and pretty much the entire Financial industry) is recalibrating their appetite for risk.

However, when cutting credit you will inevitably make people unhappy. So they would be wise to figure out a way to make the process more personable than the horror stories we sometimes see on here.