If the system is sending me a notification, it must already know I have a calling card - else, *everyone* that logs in or out of SL is causing the system to send updates to *everyone* in the hopes they have a card!

If the system works as you've described it, deleting the cards has no effect anyway. Since you say the system searches through my entire inventory for the card, it obviously doesn't know that I have it ot not. I'm probably still going to get the notifications, card in inventory or no.