I have all my photos on external NAS storage. But often, I'm on the road with my laptop. It would be cool if I could mark folders as "available offline", so I could continue to work on the road where I don't have access to my NAS device. It would be more transparant and also faster and easier than a manual drag and drop from the NAS to the local harddisk. Also, people at home could continue to have access to the files on the NAS. Now, they don't, cause I've moved the folder to my local harddisk.