Yeah, well, the building will still be there in an hour, tomorrow, next week, next year, and 20 years from now. One can always go back and get another shot, or better shot, should a card fail. Not so with weddings, ball games, etc. I've never had a card fail either, but I do mostly portraits and almost never for a special occasion. The times I do a lot of shooting, fashion shows and model boot camps, I am happy to have an extra card recording the shots. In cases like weddings, fashion shows, model boot camps, nuptial boudoir, etc., a card failure would be a disaster. I'd hate to hang my reputation on, "Oops. Sorry." I'm not even a pro, but I still run in some circles where that would be ruinous. If I were an architectural photographer, maybe one slot would be "okay". However, I would imagine some shots could take quite a while to perfect. Losing work because I was too cheap to spring for a $20 card just would not make sense... if I were a pro. Seems like real inexpensive insurance to me. (plus the expense difference of a 2 card camera). To be honest, I have started putting each model on a separate backup card of her own.