How does a tweet die? Quickly and quietly. As any Twitter user can attest, the rolling, unstoppable "tweet stream" has a short shelf life; any message older than a few hours has reached its expiration date. That all changed yesterday, when the Library of Congress announced (through its Twitter account, of course) that it would archive every public tweet ever made. That’s right—every tweet, from the mind-numbing review of your sister-in-law’s breakfast burrito to John Larroquette's 140-character tone poems, will now be preserved for posterity.

This is good news for pretty much everyone. It's a win for Twitter, which gains legitimacy at the expense of its rivals. (Don't expect the Library of Congress to target Foursquare checkins any time soon.) It's a PR coup for the Library as well, showing the world that a hidebound government bureaucracy can adapt to the digital era. And, most of all, it's a boon for researchers and historians. Much of Twitter is drivel, but a smart data miner can glean truth from this mass of information, which one Twitter executive characterizes as the "the pulse of the planet." Individual tweets may prove worthy of historians' attention as well. The Library of Congress points out that Barack Obama’s tweet about winning the 2008 election is worth preservation. And if, say, one of today’s young Twitterers becomes president in 2028, historians will be glad to have a Twitter timeline of his or her early years. (As will muckraking journalists.)

In fact, the only group that might be a little discomfited by this move—other than Tea Partiers angry at the fact that the government is doing anything at all—are the Twitterers themselves. We’re quickly approaching a world in which most of our thoughts, writings, pictures, and ideas are stored permanently in a digital warehouse somewhere. Most of us recognize this at an intellectual level, but we don’t always act accordingly—society is still in an in-between zone. Already there are a smattering of cases where a dashed-off tweet caused controversy—see, for instance, the ABC News reporter who tweeted about President Obama calling Kanye West a “jackass.” The presidential candidates of 2028 might not want to give the press access to the digital artifacts of their young selves. But increasingly, they don’t have a choice in the matter.