I got a replacement Amex card (after some fraudulent charges) 4 or 5 months ago, and it had an all new number, not just a few digits.
This card also had the embedded chip, so that may be why it had the new number.
This card also had the embedded chip, so that may be why it had the new number.
It would have been as much software update to have implemented PIN and would've brought security to the level of ATM cards.
The generation and provisioning of card numbers is limited by other systems which includes fraud detection, account processing, auditing and other backend systems.
In every case were I used a USA chip card (with no PIN), the card reader prompted for a signature, so it was no problem.
Though I really don't understand why USA issuers and merchants went with a chip-only system, seems like it would have been trivial to allow PIN too.
Though even Chip and PIN only fights a small portion of the fraud - every time I've experienced credit card fraud, it's been with internet purchases. Amex used to let me generate a temporary card number for each merchant, I used that all the time, but they dropped the service for some reason.
It's also a great deal more difficult to extract the secret information from the chip; I don't know if anyone has done so yet.