I explained this before but nevertheless again not a problem. Typically I am already owning a pre-built NAS which has two 1TB drives giving me lots of space. I used to keep my FHD movies, MP3, Photos all inside it alongwith semi HD movies, TV Shows etc. Now I have a network of friends and relatives with whom I regularly exchange items. Since I cannot give them the entire NAS box I end up copying the friend's preferred items into a USB Portable HDD and give it. If he has something to give me in return I have to copy them again inside the NAS to be able to share them on network again, tomorrow if I run out of space on the USB Portable drive I remove some or all files and re-copy fresh ones for sharing with friends once again. I want to avoid this extra bit since I already have 1TB External Drive and planning to get another 3TB the advantage being I can easily carry these to somebody's place for give-n-take. Having this Synology or similar product relieves me of all these hasstles as I can instantly put new items on share on the network typically like Hot Swappable drives. Moreover this having built in UPNP server can stream to PS3, TV directly. Hence the keyword is convenience.