i simply heard about this in a computer security class, and one of the triggers if i remember correctly was via GPS location, and no i wasn't speaking about it as a backup solution i was simply replying to
H_TeXMeX_H's tangential information

back on the original topic i would say tapes are the most reliable albeit not random access

About flash drives being permanently inaccessible once they fail: do they fail randomly, regardles s of how often they are used? If I copied data to a flash drive once and then put it away, would it stand a good chance of failing for no apparent reason while in storage?

No, flash drives fail after some time of use, but you never know when. If you wrote data to it once then kept it safe, I'm quite positive there would be almost no chance of data loss (as long as it really is safe, and it wasn't a bad drive to begin with).

CD/DVD + DVDisaster for some data (mostly audio video), rsync-based incremental backup on hard disk for everything else (documents, mail…).

Yves.

If you are a business and your data is so important then it might be an idea to backup to tapes and then look at some off-site storage. Many companies provide this but it is expensive.

or a safe deposit box ... ?

Our company uses these:

http://www.deepstore.com/

Nope, I'm just an insecure user who thinks his computer might be stolen at any time.

I have decided to stick with CDs, just because I don't feel like spending money for a flash drive. (I know they're cheap, but I still need to pinch pennies.) If you were going to store a hidden backup CD somewhere away from the computer, but might modify the contents once in a while, would you use CD-Rs and keep replacing them, or use a CD-RW? (I don't have a DVD-RW drive, and don't have enough valuable data to need DVDs anyway.)

I'd be wary about using cd's - the dye degrades over time - make sure you get a good quality disc and store in the dark. I would write a new cd but don't throw the old one, keep an incremental backup.

Tape - no question. I still have backup tapes I created over 30 years ago. They sit in a cardboard box in my office in a sub-tropical environment. And they were still readable a year ago. Real (as in reel) tapes mind.
For home I like dvdisaster or fsarchiver - because they check the data. This cannot be over emphasised given the crap media we will all be using.

As for the comments re flash - I think a lot are confusing flash sticks and ssd. You *really* don't want to have a ssd fail ...

Use only CD-R for backup purposes. CD-RW are not reliable enough for backups, in fact they're hard to find nowadays for some reason, or maybe it's just the area I'm in ? Either way CD-RW will not last as long as CD-R.

Thanks, I needed that information. Well, since computers often don't even have floppy drives anymore and their capacity is small, CD-RWs are pretty good for zooming information between computers if you don't have them networked.

... or USB stick.

Another consideration is the price, I just bought a damaged 100 spool of CDR for 8.00 USD. There were nine broken and I figure that makes them cheaper than the old floppies.