Wow, I'm surprised that everyone is in the "don't sign" camp. For one thing, if you don't sign it and someone steals it, then they can put their own "valid" signature on it. But the main reason you should sign is that it's part of the credit card agreement. You're in violation of the terms if you don't.
From Visa's merchant agreement (PDF, p 33). Bolding mine:
"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.
The words “Not Valid Without Signature” appear above, below, or beside the signature panel on all Visa cards."
They never caught me yet.... I am a rebel. And, when I got my new mattress, I cut off the tag. That's how I roll.
In all seriousness though, I just stopped signing them because I wanted to draw attention from the clerk, cashier, waitress, etc. to check my ID, but fails every time anyway.
“Beware of little expenses. A small leak will sink a great ship” – Benjamin Franklin
Gardening since 3-26-15
I don't with the hope they will ask for ID if it's ever lost. But with the abundance of debit cards you just swipe it yourself and sign the slip, the cashier hardly ever touches the card anymore.
I used to write "See ID" on my cards a few years back, but now I just sign it because it really doesn't make a difference. There have been many instances where I have opted to use a credit card for a large purchase and nobody would compare signatures/request photo ID. The only card I won't write anything on is the BCE because I think it looks sleek without it.
On all my cards I write "see id." In most cases the clerk never ask to see my ID and the ones that do notice it I always tell them thank you for asking.