EDIT: I read too quickly- this only applies to Membership Rewards cards, not cobrand or other credit products. I would not be surprised to see this policy roll out to other cards in the future, however.
http://frequentmiler.boardingarea.co...ming-heats-up/
Saw this in my FT digest email today- seems Amex is looking more closely at spending patterns, including, notably:
Very large credit card spend that far exceeds a person’s apparent ability to pay. My guess is that they will watch this more closely with personal cards than business cards since large business purchases are common and normal.