One advantage of being an Apple customer is that there's an very helpful community of users that offsets some of Apple's "industry-standard" quality control issues. On an Apple iBook forum an expert aide points out my iBook's apparent drive failure may well be a logic board failure. Here's what I wrote back:
Ronda,F/U to come.
Thank you so much. I thought this was a hard drive failure, but I started the iBook in target disk mode and thrashed it (SMART didn't work in this mode). I repartitioned, erased, put on a DOS partition, erased, put on a Mac partition, copied 15GB of data to it -- the drive never hiccoughed.
I then cloned a backup image  and the system ran -- sort of. A Retrospect restore worked for a while, then stopped. On one restart I got a blank blue screen -- but a remote computer indicated the retrospect client was running. On another restart I got the disk not found (again).
I've reset nvram from open firmware boot and, especially, after the various repartitionings, erasures and original CD reinstalls I'm sure there's no software or drive data corruption remaining.
So I've eliminated software and I'm increasingly confident that the drive itself is ok. That does tend to implicate the logic board.
Of course the program ended March 18th, 2005 or 3 years past purchase -- and my system was purchsed June 2002, so in theory I'm out of range. Of course I'll call anyway.
 I've survived at least 4 major drive crashes over 15 years with very little data loss -- I have backups like some people have shoes.
Update: No luck with Apple! They charge $50 to talk to a product specialist, $200 or so to look at it (and if it doesn't have the original 128MB memory stick they send it back unfixed!), and more beyond that.
First Tech Computing, a local authorized Apple dealer, will charge $40 to look at it and then will tell me what a repair costs. I'll pay for First Tech, and if I end up having the logic board replaced I'll take phone Apple Customer Relations at 800-767-2775.
Update 7/30: The very last thing I did was to create two partitions on the iBook, 1GB and the rest. I cloned to the "remainder" and left the 1GB empty. It's still running. I think the effect is coincidental (ie, the problem will recurr), but it's interesting. I'd hypothesized that if there is a drive problem, it might occur in the heavily used initial portions of the drive and that this maneuver might shuffle critical files out of that area. I'm using the iBook purely as a "thin client" for now.