Memory is an interesting topic in psychology for a myriad of reasons and is certainly among those capabilities of the brain which are not well understood today. For example, why is it I can remember people's faces but not their names, or the reverse, without constant interaction with that person (and in one case, even then I could not remember the name). Now researchers at the University of California, San Diego, as reported by Springer, have found that, for some reason, Facebook posts are extremely memorable.
The researchers compared the memorability of Facebook posts to that of sentences from books and human faces, and found that the difference can be as striking as that "between amnesiacs and healthy controls." In an effort to understand this, the researchers attempted to control for social thinking, which would add links to the memories and improve their memorability. (For example, reading a post about something a friend or you did.) That potential linking failed to explain it. They next examined if it could have to do with how coherent and complete the ideas in Facebook posts are, but again that failed to explain the result.
Ultimately the researchers believe it is a combination of factors which are causing Facebook posts to be as memorable as they are, or perhaps something deeper. Another potential explanation is that Facebook posts from ordinary people are better able to tap into our mind's basic language capacities. Essentially, maybe the sentences are so simple that it is difficult to forget them.