Every public tweet, ever, since Twitter’s inception in March 2006, will be archived digitally at the Library of Congress, the largest library in the world.
I’m still totally puzzled by how a so simple service (basically you can post 140 chars of text and nothing more) got so widely used! A typical Matthew effect (the rich gets richer)!
See more on official Library of Congress blog post “How Tweet It Is!: Library Acquires Entire Twitter Archive”.