American Express has flipped the Centurion Card back to being invitation only. Originally the card was launched as invitation only as was the platinum card, as of a few weeks ago American Express has now changed the Centurion Card back to invitation only regardless of spend.
Centurion New Accounts
M-F 8AM – 9PM EST
Sat 10AM-6PM EST
There’s a discussion over at Flyertalk on this as well.