So my iPhoto has become essentially unusable.
For image files, this only happens when you select them to do something with them, but apparently there's a bug in iPhoto in which if you have a movie file on an unmounted disc, it immediately looks for it at startup of iPhoto and hangs up with the Spinning Beach Ball of Death unless you have the volume available. This created a bad situation where iPhoto gets stuck looking for files that it can't find because their volumes aren't mounted. I ran out of space on my powerbook, and started burning pictures off to DVD before importing them, with the "copy files to library." feature turned off.
It takes a very long time, is non-destructive to the current library and requires space on the disk for a complete second copy.The resulting library is 2 MB smaller than before (mostly due to cleaned up thumbs and smaller.This did not result in lost data but did mess up the roughly chronological flow of my library.
Some rolls that apparently had no date information were put at the end of the library with the current date.Albums were maintained but "rolls" were completely renumbered starting from one.There were a number of orphan JPG thumbnails in the "thumb" folders that were cleaned up (deleted in the new duplicate library.).I used this and found a number of interesting things that happened: Clicking OK will allow you to select a new location for your library (make sure you have enough space).
Press Shift-Option while starting up iPhoto to invoke it, and you will get a rather scary message about possible loss of data if there is any unreadable data. IPhoto has an undocumented "Rebuild libary" option.