From the Visa site:
"?See ID? Some customers write ?See ID? or ?Ask for ID? in the signature panel, thinking
that this is a deterrent against fraud or forgery; that is, if their signature is not
on the card, a fraudster will not be able to forge it. In reality, criminals don?t take
the time to practice signatures: they use cards as quickly as possible after a
theft and prior to the accounts being blocked. They are actually counting on you
not to look at the back of the card and compare signatures?they may even have
access to counterfeit identification with a signature in their own handwriting.
?See ID? or ?Ask for ID? is not a valid substitute for a signature. The customer
must sign the card in your presence, as stated above."
"Requesting
Cardholder ID
When should you ask a cardholder for an official government ID? 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. Laws in several states also make it illegal for
merchants to write a cardholder?s personal information, such as an address or
phone number, on a sales receipt."
"Unsigned
Cards
While checking card security features, you should also make sure that the card
is signed. An unsigned card is considered invalid and should not be accepted. If
a customer gives you an unsigned card, the following steps must be taken:
? Check the cardholder?s ID. Ask the cardholder for some form of official
government identification, such as a driver?s license or passport. Where
permissible by law, the ID serial number and expiration date should be
written on the sales receipt before you complete the transaction.
? Ask the customer to sign the card. The card should be signed within your
full view, and the signature checked against the customer?s signature
on the ID. A refusal to sign means the card is still invalid and cannot be
accepted. Ask the customer for another signed Visa card.
? Compare the signature on the card to the signature on the ID.
If the cardholder refuses to sign the card, and you accept it, you may end up
with financial liability for the transaction should the cardholder later dispute the
charge."