James Bridle decided to collect all his Twitter messages from the past two years and print them up in a hardcover book. He will make one for you, "if you ask nicely and pay me a lot of money."
Why do such a thing? Bridle explains, "When Twitter is inevitably replaced by something else, I don't wan to lose those incidentals, the casual asides, the remarks and responses. That's all really. This seems like a nice way to do it, and I'll probably do it again in a couple of years."