Actually, the industry is going MORE to using hard drives for backup devices, depending on the type of backup. SAN backup solutions are increasing in popularity for example for daily backups. Archives however still typically are tape.
Whether it be a "true" backup or not really depends on how up to date the backup is, how long it takes to restore the backup, how likely the backup could be bad, etc. It doesn't matter what you backup to, whether it be CD's, DVD's, hard drives, tapes, or floppies. In backups, the more valid backups (or more likely to have a valid backup), the amount you can backup given the media and time it takes to backup the data, where the backups are stored, those are what to consider when choosing a backup.
Let me give an example. If you have 10M worth of word docs to backup, which is the better solution - one tape backup of them, 2 CD's of them with one offsite at all times, or 2 USB pen drives, one kept at a different site? The pen drive solution is the most fullproof backup out of those. Throughput is faster, you could change the data faster than erasing a CDRW, or less costly because you wouldn't have to keep using up CD's. USB pen drives are the most reliable physical media media out of those three choices. It would easily accomodate the anount of data needed to backup. You've prevented "acts of god" by having an offsite backup. Who cares if many wouldn't call a pen drive a "true backup"? In this case, it would have been the best backup solution for this situation.
As far as efficiency goes, hard drive backups have boatloads of more throughput, so you can backup more in less time. This is why daily backups in large companies are going more to hard drive backups in SAN's, called "snapshots". This reduces the time it takes to backup everything daily, which helps those large organizations because they often have terrabytes of data to backup.
A hard drive device on its own is often more reliable than a tape backup device, but the problem is expandability and redunancy in your backups. You can simply add more tape cassettes to add to the number of physical media you have backups on. Hard drives you would need to buy additional hard drives, which is more expensive in the long run.
Irregardless, the hard drive to which you're backing up should NOT be local to the computer unless it's external, and it should then be disconnected after the backup is completed (same thing as taking the tape out of a tape backup device). You should also have as recent a backup as possible OFFSITE from your organization, in case the building burns down or other "acts of god" that might destroy your data, whether it's a tape or hard drive type device.
Keep an open mind when choosing a solution to fit your specific needs. How much data do you need to backup? How much time can a backup process take that's acceptable to you? How much money can you spend? How long can a restore process take should something happen? What kind of data needs to be backed up? (Applicable to constantly changing data in say a database like SQL or Exchange email server.) How much is the data you're backing up expected to grow in the future? How much data can you afford to lose?
"...but in my defense, it was dark, I was drunk, and it was delicious!"
