Re: I don't get NAS boxes...
"...Why not build a Win 7 / Win 8 PC with shared libraries,..."
Why use Windows? It is not safe and susceptible to data corruption. Ever hard disk gets lots of read/write errors during normal usage, but gets corrected on the fly with error correcting codes on the disk. However, some of these errors are not correctable by the codes. Even worse, some of these errors are not even DETECTABLE by the codes. The codes are not fool proof, you know. They might be able to correct 1 bit errors, and detect two bit errors, but sometimes three bit errors happen. Very rare, but they happen. And those three bit errors are not correctable. Sometimes four and even five bit errors happen, and such errors might not even be detectable. This is called Bit Rot, google on it. Old VHS tapes doesnt work today, the data has begun to rot.
It is exactly the same problem in RAM. Why do you think servers need ECC RAM? ECC RAM can correct 1 bit errors, and detect 2 bit errors. Microsoft concluded (after collecting information about Windows crashes) that 30% of all Windows crashes was caused by random bit flips in RAM, something that ECC RAM would have protected against. Cosmic radiation is a big source of random bit flips, flaky power, sun bursts, etc. There are much research on data corruption.
You need a solution that always calculates checksum data of every read block on the disk, in effect doing a MD5 checksum on every read. Or SHA1, or any other checksum. This is the only way to protect against bit rot on disks. Incidentally, ZFS is designed to protect against bit rot, and does exactly that: for every block you read, it calculates a SHA256 checksum. And if the checksum is not correct, it automatically repairs the block from the raid. And, ZFS is free, as in gratis. If you try ZFS, you must not use hardware raid, because they mess up the checksum calculation. Sell it, and use free ZFS. Here is much research on data corruption on disks. And of course, if you are serious with your data, you should use ECC RAM too.
NTFS, ext, HFS, XFS, JFS, etc is not safe, and might corrupt your data (research paper) here. And ZFS is safe, according to researchers.