All USA-issued American Express charge cards have no preset spending limit, as do many MasterCard and VISA products. American Express markets this as a benefit to the cardholder, and it can be, but it is also a benefit to American Express because they have not contractually agreed to any limit and can decline any transaction.
Hah I never thought about it that way, and it's quite interesting.
Well the spending pattern needs to be analyzed from AMEX standpoint and I remember cause it was quite painful at the beginning, I had to pay in advance almost everything to be allowed to charge what I usually charge on the card, etc... after a couple of months, it worked. I don't know how the spending pattern is calculated but in my mind, you are always going to have exceptional charges you want to be able to charge on the card, and that would put you way above the "normal" spending pattern.