WTF is link rot?

Academia has taken note. Last week, Harvard’s Berkman Center released Amber, a WordPress and Drupal plugin designed to help websites keep linked content accessible by storing copies of Web pages. If a linked page goes down, Amber serves the cached alternative. Here’s a primer on link rot and why it’s a problem many see as worth fixing.

So what is link rot, exactly?
It’s not too complicated. Link rot is a somewhat dramatic name for broken links. It’s a vital topic for anyone concerned with the perseveration of content on the Web.

OK, so “404” errors. What causes them?
Blame technology, or more likely, human error. Link rot can happen when a site migrates to a new CMS or link structure, which can break links to old pages. Sometimes sites go offline completely, taking all of their links with them. The most common cause of link rot, though, is human intervention. Links break on the Web because sites take content down. BuzzFeed, to use a recent example, deleted thousands of posts in 2014 because they no longer reflected its updated editorial standards. That’s just one prominent example, but the problem is more widespread.

So why are academics so obsessed with this?
Academia, at its core, is built on citations. When building a case, lawyers and academics have to not only show their own work but be able to show and link to previously published work that supports their conclusions. But doing so is harder to do on the Web when websites are constantly changing and when it’s almost effortless to pull content down. It’s enough to make an academic long for print, where this problem doesn’t exist.

I still don’t get why this is an issue. It seems tiny. Give me some numbers.
It’s not a tiny problem at all. Wikipedia, for example, says that over a 130,000 its entries link to pages that are no longer there. Likewise, a 2013 Harvard study found that 49 percent of the hyperlinks in Supreme Court decisions don’t work.  NPR called link rot a “virtual epidemic” in 2014.

“Epidemic” might be overstating it, but I get your point. This is the part where I ask about solutions.
There’s been no shortage of attempted fixes to the link rot problem. The one most people are probably most familiar with is the Internet Archive Wayback Machine, which has achieved 464 billion Web pages over the past 20 years. Other attempts include the academia-focused Perma and the aforementioned Amber.