Missing the point
From my personal experience:
TAPE -- PRO: easy to maintain, easy to configure backup software; CON: Prone to failure in dirty/dusty environment, typically shorter recommended life than disk-based storage
EXTERNAL USB -- PRO: relatively inexpensive (when compared to tape's total cost); CON: drive lettering issue, difficult to configure backup software, Windows refusing to "let go", USB overhead
MOBILE RACKS -- PRO: inexpensive; CON: drive lettering issue, difficult to configure backup software, Windows refusing to "let go", poorly-designed racks can cause integrity problems
Remember, this is about corporate backups, not home backups. This is about using a set of drives as you would a set of tapes, so all drives must use the same drive letter (or you'll have to configure your backup software with a different configuration/backup set for each drive). View this as a zip drive with a really large capacity.
The drive lettering issue isn't a deal-breaker. But if you forget about it when using new cartridges/drives, or if Windows randomly "forgets" about the device and detects it as new, then it's a real problem and you missed last night's backup.
Backup software has gotten better with backup-to-disk folders and backing up to removable media, but anyone using older software will have trouble configuring the software to back up to a set of removable drives. Backup Exec 8, for example, makes it a real pain in the ass.
And the biggest issue I have found with any type of removable drives (USB or hot-swap mobile rack) is Windows refusing to "let go". Windows claims that files are open and it's not safe to unplug the drive. Even when Process Explorer shows no files open on the drive, Windows will still not let go. So you have two choices -- 1) unplug the drive anyway and risk data corruption, or 2) shut down your server so that you can remove last night's backup. Neither one of these are really options for any business.
I like the concept of backing up to hard drives. But in my experience, the hassle isn't worth it unless tape fails (such as if the server is in a dirty/dusty environment). As for the people complaining about the cost of the system, have you ever looked at a decent tape drive? A Quantum DLT-S4 800GB/1.6TB drive will cost you about 3,300 USD, with the tapes costing about 85 USD each. So no, compared to tape (which this is designed to compete with), it's not expensive at all.
The recommended replacement cycle for daily-usage tapes (meaning five tapes per week, each tape used once per week) is only one or two years. So it's certainly more than the "couple of months" mentioned in the article, but not as long as alluded to above.
The Quantum GoVault seems to be very much the same concept, but those are only available in capacities up to 160GB, which is not reasonable for any mid- or large-sized company (and really not even reasonable for many small businesses, either).
As for these cartridges/drives being physically larger in your pocket than a tape, I don't doubt that. But I don't think they'll be THAT much larger than an LTO or DLT tape. Those things really make you long for the small size of a DDS tape.