IA is one of the most important initiatives/projects on the internet, links are not meant to change but they do and when it happens knowledge & history erodes.
Remember the 2004 Indian Ocean earthquake and tsunami?
It was the first major event that provided mainstream credibility to the blogosphere, before this disaster consumers turned to news publications for information. For the first time ever news publications did not have the info and were desperate for content, any. TV crews flew into the effected areas and started purchasing suitcases/video/still cameras sight unseen off shell shocked tourists whom were too traumatized to remember if they had captured anything.
It was also the last major disaster that occurred before the social revolution - YouTube, Flickr, Facebook, smart-phones and mainstream adoption of broadband. Back then the main way for the general public to share information was via email (which had limits of 10mb) and if they were technical or knew someone technical on their 100mb of free hosting provided by their ISP.
Now imagine you're a student, academic researcher, production assistant and you have been tasked researching what transpired. As of right now, the majority of content from 2004/the disaster is no-longer available on the internet and only accessible via the IA.
(nb: I was the guy behind http://web.archive.org/web/20050711081524/http://www.waveofd... which was the first emergency crisis live/micro blog. For what Google now has a team of volunteers doing during a crisis I did it myself with a single pentium 4 cpu, 4GB of ram, a single IDE hard drive, a ramdrive, a 100mbit uplink and a week without sleep. WOD will be relaunching within the next couple of weeks and was one of the sites recovered from the IA.)