Linkrot is a serious problem, but a more troublesome problem exists in the form of content drift.
A 2013 article in the Yale Journal of Law and Technology by librarians Raizel Liebler and June Liebert found Supreme Court opinions to be afflicted by extensive linkrot. Footnotes, they argue, are the "cornerstone of judicial opinions, law review articles, and academic scholarship" and "provide both authorial verification of the original source material at the moment they are used and the needed information for readers to later find the cited source" ("Something Rotten in the State of Legal Citation: The Life Span of a United States Supreme Court Citation Containing an Internet Link (1996-2010)"; digitalcommons.law.yale.edu/cgi/viewcontent.cgi?article=1085&context=yjolt).
Linkrot combined with content drift equals reference rot.
Predating the Internet Archive activities, in 2013, the Harvard Library Innovation Lab released its own solution to the problem of linkrot, content drift, and reference rot: Perma.cc.
In the most recent of his recurring "State of the Web" sample analysis surveys, Terry Sullivan (http://www.pantos.org/atw/35654.html) reports that, at a 6% rate of dead links, the incidence of linkrot is pretty much unchanged.
As Web design guru Jakob Nielsen sees it (http://www.useit.com/alertbox/980614.html), "Even worse, linkrot contributes to dissolving the very fabric of the Web: there is a looming danger that the Web will stop being an interconnected universal hypertext and turn into a set of isolated info-islands.
Is linkrot equivalent to incorrect citations, as columnist Ernest Perez speculates in his TECHTOOLS column?