A portion of the cover of Orwell's 1984 by Signet (NetCharles.com)

In George Orwell’s book 1984, the Memory Hole was chute, down which workers at the Ministry of Truth would throw old news articles, books and documents that contained evidence contrary to the current (and frequently changing) position of the Government. Articles, documents and books were rewritten so that the frequently changing positions of the Government had always been true in the eyes of the public. The chute led to an incinerator where old evidence was instantly destroyed.

Today’s widespread use of electronic media creates the very real possibility that if data archives were held by only a small number of individuals, they might be able to edit, revise, or delete documents to suit their interests. The effect would be the same as that of the Memory Hole in 1984: the new prevailing opinions of those individuals would always have been true and the evidence to the contrary could disappear without a trace.

The best defense against such a thing would be to ensure many people hold copies of the same documents on personal hard drives – especially when engaging in “cloud computing” whenever the “cloud” is controlled by a major corporation or the government.

Wikipedia: Memory Hole