A nice little video tutorial by HolmesInFive, on how to deactivate all your PS3/PSP/PS Vita, now whilst this can be done on the console itself, it cannot be done if the console has broken or if you shared one of your account slots and that where this tutorial will come in handy.
How To Deactivate All PS3 And PSP Consoles - YouTube
How To Deactivate All PS3 And PSP Consoles - YouTube