Restored image misbehaves without LaunchServices rebuild

[Derekasaurus]

A recent thread discussed strange problems some 10.4.10 users (including myself) have encountered after restoring an SD! backup. The issues include messed up dock icons, applications not starting properly, and links pointing to random resources instead of their true targets. Fixing these problems only requires rebuilding the LaunchServices database, but I have to say my faith in the exactness of my backups has been somewhat shaken. Can anyone explain exactly what the problem is and why rebuilding the LaunchServices DB is required after restoring in some cases? I think I'd feel better if I understood exactly what the problem is and why my restored image didn't behave exactly like the original.