Is it okay or not okay for the clerk to request ID when a credit card is used?

From Visa: "Although Visa Rules do not preclude merchants from asking for cardholder ID, merchants cannot make an ID a condition of acceptance. Therefore, merchants cannot refuse to complete a purchase transaction because a cardholder refuses to provide ID. Visa believes merchants should not ask for ID as part of their regular card acceptance procedures." And MasterCard has a page where they accept "merchant violation" reports against merchants who "require identification." Therefore, merchants cannot require you to show ID when you use a credit card. This practice is against their merchant agreement. See the Related Links for "Mastercard Merchant Violation" page.