I just finished reading Animal Farm and found a great quote attributed to Orwell by Wikipedia.
The sinister fact about literary censorship in England is that it is largely voluntary. … Things are kept right out of the British press, not because the Government intervenes but because of a general tacit agreement that ‘it wouldn’t do’ to mention that particular fact.
He was speaking sometime around World War II. Someone on Slashdot the other day said that only governments censor, because only they may do so by force. They suggested that other people simply make choices about what they wish to publish. Apparently the author of 1984 thought about it a little differently.