optical drives will be obsolete in a very near future. it will be replaced with flash memory. heck, nowadays even a card reader has 512MB capacity at least, and a card the size of a finger nail that can easily store 8GB of data is not that uncommon. that's equivalent to 2 single layer DVD.
most softwares, music, and videos are now sold (downloaded) via internet. some vendors even starting to sell softwares via read-only memory card.
i can't remember the last time i use my CD drive. my blank DVD stack has been collecting dusts since forever now. why would people need to burn DVDs anyore while they can easily and quickly copy stuffs to their keychain usb drive anyways? it doesn't make sense. and why would they backup their data on DVDs while they can do it much faster and more reliable with harddrives.
furthermore, storing backups on harddrives (or NAS for that matter) makes it much faster and easier to access, as opposed to dividing your data on tens if not hundreds of DVDs and take them in and out and in and out whenever you need access. it's a very tedious process. it is surprising it isn't obsoleted yet.
i really hope the next Macbook Pro won't have optical drives at all. you can do a lot more useful things with that extra space.