Using libtar, librar, and libzip (libzipios) can be used to open archives transparently.
It would be pretty useful to be able to dig into .tar, .tgz, .zip, and .rar files and view the images without having to uncompress everything.
Storage of large numbers of images in a single file is much preferred to individual files. I imagine you could get quite a bit more on CDs and DVDs, but I have never tried for a comparison.
I would expect read-only access, but libtar and librar are pretty friendly toward read-write. On the other hand, once I've tarred my images up I usually don't want to write to them anymore. I guess that's what chmod is for.
