Just out of interest and maybe for others knowledge.
I formatted my SD card when I got my camera 3 and a half years ago. Have used the same card ever since and never formatted it again. No problems so far (touch wood). I take the card out of the camera an shove it in the computer if that means anything.
On the other hand I've seen others mention they reformat the card every time after transferring photos from them.
Any thoughts?