This is of no surprise to me as the social media companies are interested in currency not the past. Neither do their business models encourage archiving of user content no matter how trivial it would seem to be to implement (according to some of those commenting on this article).
History, As Recorded on Twitter, Is Vanishing From The Web, Say Computer Scientists, http://www.technologyreview.com
They found that the older the social media, the more likely its content was to be missing. In fact, they found an almost linear relationship between time and the percentage lost.
The numbers are startling. They say that 11 per cent of the social media content had disappeared within a year and 27 per cent within 2 years. Beyond that, SalahEldeen and Nelson say the world loses 0.02 per cent of its culturally significant social media material every day.
The study is here: