Shut Everything Down - Barack Obama Just Won The Internet

[Ravenshire]

From your own link:

As long as you've signed the card, you can tell the clerk to mind his own damned business.

Yes, but there is discover card too.

Yeah, and their five percent market share makes them a real driver in the industry.

Also, from your own article, again (my bold):

Discover’s policies are more situation-based. They state that a store employee who has doubts about the validity of a card should “request and review additional identification” from the customer, as a best practice, according to a Discover representative.
If the store employee is unable to verify the cardholder’s identity and has reason to suspect fraud, he or she should contact Discover directly.  If a card just isn’t signed, Discover requires two pieces of identification, including one government-issued photo ID.
American Express is more vague. It requires merchants to “verify that the customer is the card member,” but its rules make no direct mention of requiring an ID.
“American Express doesn’t really have a policy on it,” says Linda Sherry, director of national priorities for Consumer Action. “If the merchant wants to ask for an ID, that’s fine.”

So, we've covered all four cards and as long as the cards are signed there is no requirement for checking ID.