I sold my 3GS on Ebay and I'm debating if I should include the SIM or not? The phone is already deactivated, can it really hurt to include the SIM card? Does someone expect a SIM when they buy a phone used?
To reiterate Macguru311, no you should NOT include your SIM. The SIM is linked to your AT&T account, not the device. Depending on your SIM's history (ie the devices it's been in) it may contain personal data and information.
Anyone purchasing a used phone would need to use their own SIM supplied by AT&T.