Just an FYI, "SIM" stands for "Subscriber Identity Module." That means that SIM card represents you as much as a driver's license or credit card would. I'm certain that you wouldn't give those away if you sold someone your car or pass a wallet down to someone, even if the card is expired or deactivated. If at any point the SIM card was tied to you, the you should keep it and/or destroy it, as it wouldn't benefit the next user of the phone you're getting rid of. They will have to activate their number on a new, unprogrammed SIM card (in this case, a micro-SIM card).