If I move a cf card from one digital camera to another, is it necessary to reformat it first?

(I meant reformat!)

It is not always necessary, but it's a good idea. I move CF cards between Canon DSLRs without reformatting without any problems, but if I were to use the card on a different type of camera (such as a Nikon), I'd reformat it to help ensure that there aren't any file system problems that might lead to corrupted or lost photos!

Thanks! I moved a card from a Canon 10D to a Canon Rebel Xti, had some problems--with corrupt and lost photos-- and someone suggested that it was because I had not reformatted. I wanted to get a second opinion.

I am just learning to take semi decent photos and appreciate your help.