WASHINGTON — A Friday tweet by a Twitter user called “mcspill” proclaiming Starbucks breakfast sandwiches “yummy” could hardly have been more mundane, but even it could prove valuable to someone, somewhere down the line.

That’s the theory behind the Library of Congress’ kickoff of a project to archive all messages — or tweets, as they’re known ‚ sent over the popular social-networking site.

The project was announced during Twitter’s developer conference this week.

The privately held company also provided some statistics and details about its market for the first time. Among the most notable: It has nearly 106 million registered users who send about 55 million tweets each day.

Garnering more media attention, it also unveiled a model to increase revenue by selling ads embedded in its tweets. See full story on Twitter’s ad-revenue plan.

But for the Library of Congress, the hope is that its Twitter archive will give future researchers a new tool for studying the everyday lives of the world’s population.

That means some future scholar might pore over every last one of your tweets — from your #followfriday recommendations to your 140-character reaction to President Barack Obama’s election victory.

The Library of Congress says it has no plan to archive other social-media sites. Twitter’s 140-characters-or-fewer requirement makes it well-suited to the library’s capacities.

Studying these tweets can allow for researchers to take the pulse of what people were buzzing about and could make for interesting anthropological studies, said Matt Raymond, communications director at the Library of Congress.

While the details of this partnership are still in the works, such a move has implications for Twitter, tweeters and society. Here are seven things to know about the joint project:

* The library will archive only public tweets from March 2006, the date that co-founder Jack Dorsey pushed forward the first-ever tweet: “just setting up my twttr.” If you hide tweets from the public Twitter site, they will be ignored by the Library of Congress. No word though on whether deleted tweets will make their way to the archive.

* Your tweets will make their way into the world’s largest library sometime between now and the autumn. Twitter is expected to hand over four years of data from March 2006 to April 14, said Raymond.

* There will be a six-month delay between a tweet’s entering the public sphere and entering the library’s collection. While there aren’t many specifics about how the project will work yet, the two parties agreed to create the six-month window before tweets go into the library’s research archive. “It’s not a real-time type of thing, like if you were to create a hash tag right now or if you were to look at what was a trending topic,” Raymond said. “This will be a mint-edition copy of Twitter for posterity, for researchers, so people will be able to go back and slice and dice the data however they want it —by year, by keyword.”

* Archiving all of Twitter will take less than 5 terabytes of space. In contrast, the library has about 167 terabytes’ worth of online content from the last 10 years. Raymond said that because hard-drive space is cheap, the tweets will hardly be a crimp on the library’s resources. He noted that the library is well-equipped to archive the collection of tweets; it digitizes 3,000 to 5,000 terabytes of audio and video collections each year.

* There are no plans to archive any other social-media Web sites at the moment. Twitter is an easy project to undertake because of the lightweight nature of 140-characters-or-fewer microblogging. Facebook, on the other hand, is a much more difficult medium to archive. “Facebook is characters and videos and pictures and different levels of privacy settings,” Raymond said. “It would be vastly more complex.”

* The Twitter archive could be a valuable tool for historians and even archaeologists. “We’re getting a sense of how people saw the world, how they saw themselves, their society, what was important to them,” Raymond said. “It’s just a new type of technology about people documenting our society and what life is like at this time in history, just as letters and journals and photographs and maps were in previous centuries.”

* Knowing your words go on public, permanent record means you should be smarter about what you tweet. While Amanda Maurer is intrigued by the notion of recording the public’s thoughts, the Chicago Tribune’s digital news editor said the Library of Congress undertaking means people have to be more strategic about how they convey their online personas. “They need to be aware of what can happen,” she said. “You need to be really smart about what you say, watching what you say about your job or your co-worker.”