Sony now has two different RAW file formats available in the A700. What happens if everybody likes the new format, and Sony doesn't include the old format in future cameras? What happens when software developers get tired of developing for two SOny RAW formats and decide to only support the newer one.
What about NEF files? Nikon had a RAW file format for it's early dSLRsm, but then introduced a new format in a new camera, and the RAW file was encrypted? Public pressure caused them to provide SDKs for the newer, encrypted format, and now everybody supports it. But what happens when all those software developers get tired of supporting the older format?
This kind of stuff happens all the time, but it takes years to see the actual effect. There are still software developers that are distributing software updates and license keys via floppy disk! That had its advantages and its disadvantages, but since you can hardly buy a PC with a floppy disk drive anymore, someone else has made a decision for you. Now, you can't consider the advantages and disadvantages of floppy disks any more.
If you back up your photos on mulitple media, why would you not back up your photos in multiple formats as well?