I used to have a Canon Powershot S40 with a small CF card that eventually had a few "sectors" go bad. But it was a first gen flash card, in an early camera, that got a lot of heavy use. Chkdisk'ing the card mapped out the bad part and I could continue using it, although it would only hold about 70 images instead of the 100 or so prior to the failure. Had I kept using the card in the camera I'm sure the degradation would have continued. The only way I noticed it was the reduced capacity. In fact I don't recall loosing any data, just that Windows didn't want to read it until I did a chkdisk on it.