Instructions
Power on your PlayStation 3.
Log in to your user account, then go the video section and select the Netflix program. The program will start up and bring you to the Instant Queue screen.
Push the following code into the directional pad:
up, up, down, down, left, right, left, right, up, up, up, up
This will cause a new screen to appear over the Instant Queue menu, displaying your account information, and the option to either "cancel" or "deactivate."
Select "deactivate," which will log out the account.