First, @fatchap, "transported in secured containers" is bullocks as a replacement or priority suppliment for encryption. I'm sure it takes more than just a hammer to get into 2048-bit-key encrypted data.
For companies dumping their 500GB or less data to tape, and expecting it to last indefinately, they should really research alternatives. 500GB hard drives are very common, and NTFS isn't going anywhere. Also, many people have demonstrated the longevity of computers with "antiquicated" interfaces (think of the Floppy Drive, if it took that long to die, just think how hard it will be to kill USB 1/2.0, not to mention the kit that supports USB 1/2.0, and the OS to read NTFS). I say NTFS, because FAT doesn't allow for >4GB files (think TrueCrypt containers or the like). Fortunately for those using TrueCrypt for encryption, it doesn't require a license key and can install on ANY of those "old" systems that support USB and NTFS....convenient that. No more having to find some server with an ancient SCSI card (with drivers!) to hook up a dusty tape drive that probably has grime on the read-heads anyway (be sure to run a tape cleaner through it first!!!). Then loading an OS that supports the archaic (ArcServe!) software, and don't forget the license key!. Then hope that the particular file you want hasn't been corrupted due to degredations of some sort, or even worse, the index.... Hard drives aren't impervious either, but I am willing to bet that a hardly-used hard drive sitting on a shelf will degrade slower than a tape sitting in the same environment.
That said, newer tapes and devices allow for storing many terabytes of data, which is currently impossible for single hard drives, and for large organizations, tape is the only way to go. However, the best solution would be regular restores and transfers of older tapes onto current-gen tapes to overcome degredation and outdating hardware. This of course is time consuming and probably best left to that 2nd year college student that the firm is interning for the summer...
Lastly, for those "just store it online" folks, some regulators will prohibit some organizations from using such services because it can't be guarenteed to be "safe." If the data isn't encrypted locally, then shipped over an encrypted VPN point-to-point-style, and stored in encrypted form on said remote system, without the keys, then it is useless. (Uploading a TrueCrypt container to such a service would be plausible...). However, I would doubt dumping 400GB worth of data to an online service would be remotely cost-effective, let alone having "archived" copies available. And if you have to archive backups locally, why even bother with an online service anyway? (No, I'm not talking about home users with 10GB of unchanging data, saving to a service in case their house burns down. They can [and probably should] use such services, since that is for whom they are designed.).
As for CDs/DVDs/Archival DVDs, these may look attractive, but I don't trust such media to store my data unless I have two copies. I've had enough disks that get a simple scratch for whatever reason, and then become coasters. And archival DVDs rated for >10yrs are simply as expensive as their tape counter-parts, but require even more uncommon hardware.