I don't know how I missed this post, but thanks for the real world example. That's exactly the reason I like Amex. I was able to get a personal card limit up that high in something like 3-5 years of total card ownership, but maybe only like 18 months when I started asking them.
Direwolf: Thanks for chiming in. When I get around to applying for an Amex business credit card, I'll see if they use my TIEN number to pull my business credit, use my SS, or both, and if I remember I'll report back here. I was able to find a business credit rating with D&B and Experian, so at least I have some credit floating around out there.