Perma.cc: Addressing link rot in legal scholarship

I've written several posts on the subject of persistent identifiers, especially DOI, and their importance in maintaining access and enabling permanent cross-referencing and citation.  However, DOI is intended for stable objects, primarily version-of-record scholarly publications (articles, chapters, etc.).  Blog posts, websites, wikis, social media, and similar Internet content can also be useful for research, but authors are forced to fall back on including ordinary URLs when citing these sources. This problem has been specifically documented in legal scholarship--when Harvard Law School researchers recently surveyed the state of legal citations, they made the disturbing finding that "more than 70% of the URLs within the Harvard Law Review and other journals, and 50% of the URLs found within United States Supreme Court opinions, do not link to the originally cited information."

In response, an online preservation service called Perma.cc was "developed by the Harvard Law School Library in conjunction with university law libraries."  Perma.cc works like this:  if an author wants to cite a website or other online source that lacks a permanent identifier, he or she can go to the Perma.cc site and input the URL. Perma.cc downloads and archives the content at that URL and returns a perma.cc link to the researcher, who then uses it in the citation. When the article is submitted for publication to a participating journal, the journal staff check the perma.cc link for accuracy and then "vest" it for permanent archiving. Readers who click the link are taken to a page that offers a choice of the current live page, the archived page (which may not include linked content such as graphics), and an archived screen shot (which will not include live links). Sites that do not want Perma.cc to make their content publicly available can opt out through a metatag or robots.txt file; in these cases, Perma.cc will place the page content in a dark archive, accessible only to the citing author and vesting organization.  Interestingly, Perma.cc still harvests the content, even though it doesn't make it publicly available.

It will be interesting to see if this service (which is still in beta as of this writing) is successful, and if it expands beyond the legal field.  It seems to me to be an excellent companion to DOI, as DOI gets around the problem of copyrighted, toll access content by maintaining only links, rather than archiving content, while Perma.cc provides the same level of stability for freely-accessible but less stable web content.