There was a recent article in a magazine (Forbes? Fortune? I forget) about the AMEX Centurion. The idea behind the article was how 10-15 years ago a Platinum card from any issuer was high class. Gold was becoming diluted by then. Now, Platinum is available to almost anyone.
But the AMEX Black is something, according to the article, that AMEX gets many requests for and summarily turns them down. Annual spending is one big criteria, but there are other factors that weren't mentioned too. It was funny reading about the level of begging and pleading people have done to get one of these for the sheer status.