[font color=\'#000000\']I think that formatting a CF card in device A, but using it in device B, could (rarely) lead to problems. If the two devices don't share *exactly* the same definition for how-to-format the card, problems could creep in.
I have had no problems formatting cards inside my 1Ds. The camera "knows" what it expects in terms of a formatted card, and has never produced corruption of any kind.
Cards formatted in my 1Ds have also *never* failed to read correctly with my Macintosh.
And, as I mentioned earlier, I choose to format my CF card every time I'm ready to re-use it, after having saved my images to my hard drives. By doing this, I ensure that each time I start a shooting session, my 1Ds has removed all possible "unknowns" about the state of the CF card.
It's what has worked (flawlessly) for me.
Enjoy!
-- Jim[/font]