First, please don't take this as an advocation of piracy. While I like sticking it to the man as much as possible, this statement also has applications in terms of backing up legitimately-owned stuff (naturally).

I've been doing a lot of backups of various DVD-Videos lately, and found some rather peculiar traits on some films. The PAL versions of such pieces as The Rocky Horror Picture Show or Charlie's Angels come on DVD-9s, but they have one peculiar eccentricity. The actual film, once you take out the extras, unnecessary subtitles, dubs, even commentaries, will fit easily on a 4.35GB DVD-R. In the two cases above, you can fit the main feature with all the soundtracks included and still have room to spare.

Is this a sign of some wooly thinking on the part of the distributors, at least in earlier days? I remember what a big deal it was to make two-disc sets (Fight Club being the first in Australia), and you can imagine what people thought when they discovered that in some cases, the first disc utilised less than 75% of the disc space.