The Library of Congress will collect and store the full volume of Twitter for “scholarly and research purposes.” Twitter is psyched because it’s another demonstration of legitimacy:

It is our pleasure to donate access to the entire archive of public Tweets to the Library of Congress for preservation and research. It’s very exciting that tweets are becoming part of history. It should be noted that there are some specifics regarding this arrangement. Only after a six-month delay can the Tweets will be used for internal library use, for non-commercial research, public display by the library itself, and preservation.

As evidenced by events like the Iranian election protests, Twitter users can act as documentarians of history as it happens.  The Library of Congress’s recognition of this is another sign that Twitter has grown up a bit; the timing couldn’t be better, coming just a couple days after they announced their advertising model.

For the vast majority of Twitter’s data, this announcement is really a non-story – after all, there’s nothing stopping anyone from visiting Twitter and accessing all public tweets.  What about accounts that have been deleted, though?  And what about the accounts that get deleted after the Library of Congress makes an official historical record of them?

Buried in Twitter’s blog post is a much “friendlier” strategy for making Tweets a part of history: Google’s Replay service, which allows users to revisit moments in history and watch events unfold through Twitter and other online media.

As with most announcements, the difference lies in the semantics.  Google Replay would pinpoint specific times and issues – in other words, it would gravitate toward tweets which were sent with the idea that they were for public consumption.  The idea of Twitter turning over a hard drive full of information to a government office may be no different in practice or outcome, but it sounds a lot creepier.  Suddenly, you may find yourself perusing your own Twitter feed to see if you have anything to worry about.  A better announcement might have been a joint release by Twitter, Google, and the Library of Congress discussing a way to incorporate publicly broadcast real-time updates into research.  It might have looked like a tool on the Library’s website, powered by Google.

The nature of Twitter makes this a minor issue, but it isn’t the only place that history is recorded in real time.   Facebook and Google Buzz have both incorporated elements to mimic Twitter’s free-flowing stream-of-consciousness format.  That means they’re just as potentially attractive to the Library of Congress as part of the “historical record” – even though their data is decidedly more sensitive.