there is always a limit on AMEX cards. There is no such thing as no-limit with them. You still have to call in and ask if the purchase will go through. usually they give you a limit cap, say to $10,000 and that is it. Don't believe me? Just call AMEX customer service and ask.
they may have asked what I make per yr, and i told them.....that is all.
i am not sure what AMEX asked for because I talked to several cc companies the same night. I remember 1 or 2 asking if they can pull my credit report, what i granted.
when i had a 2.5 limit w/ AMEX (which i got in late 2006), AMEX did give it to me (thru actually purchases) 0% rate for some time. I had 100% utilization w/ them for months.....that may have played a part.