As Don said, prevents you from losing bulk photos if you fill it up and it fails, just buy more smaller cards.not trying to question you however what reason does it make to use 16gb over 64gb if it fails?
are you implying smaller size means uploading on computer more often ?
I will most likely set up two sd one as a back up.
I am yet to fill a 16gb card in one session, so it's not an issue to me.