Heh. Taking an archaeologist's view, unless it's carved on stone or baked into clay tablets, it's all pretty transient.
Many lesser transparency and negative materials degenerate within a twenty year period or so. That's one reason we are talking about particular, stable Kodak propriety processes.
There is a good argument we've been through a new dark age with the quick obsolescence of computer media formats - big and little elements (I can't read a 3.5in disc on anything here), a problem some organisations have found when upgrading to new systems but losing old backup / data formats.
As to the transience of the internet, it's an issue, but not as much as some think. There are archiving programmes running - in Australia there is the Pandora project:
http://pandora.nla.gov.au/about.html and stuff like the Wayback machine.
However I do think it's just missing the point to focus on the
medum specifically. As Holedigger's said, the quality of the equipment (lenses particularly) counts then and now for a lot, while the final arbiter is the person making the image. Whether talking photography or art, ancient or modern, it's the person who makes the pic, their 'vision' that makes the difference between great and good. Tools help, but great photographers have made great images with poor gear; poor photographers will still be forgotten even if they have the best equipment. (Have a look at Frank Hurley's work with his vest-pocket camera in the Antarctic in 1914 after he lost his large format one.)
Interesting discussion!