Apple has a secret list of words which it won't autocorrect to, according to a smart bit of data journalism from the Daily Beast . The site ran misspellings of 250,000 words through the iPhone's dictionary (running iOS 6), and found approximately 20,000 words which it wouldn't correct. Of those, many were boringly technical: "'nephrotoxin,' 'sempstress,' 'sheepshank,' or 'Aesopian,' to name a few."
But a sizeable minority weren't. These were words like "abortion", "rape" and "drunken", which are highly charged, but also relatively frequently used, and which Apple never autocorrects misspellings of. Other words "censored" include:
“abort,” “bullet,” “ammo,” “drunkard,” “abduct,” “arouse,” “Aryan,” “murder,” and “virginity”… “bigot,” “cuckold,” “deflower,” “homoerotic,” “marijuana,” “pornography,” “prostitute,” and “suicide.”
The breadth and depth of words included is interesting in it's own right, and I don't doubt that a student of the English Language would find the complete list a godsend for research. But, as a news organisation, the Beast has to develop some controversy around its findings, and that's where it goes off the rails:
“I hate to say it, but I don’t think this should surprise anyone,” says Jillian York, the director for international freedom of expression at the Electronic Frontier Foundation. “Apple is one of the most censorious companies out there,” she explained, and cited the company’s history of censoring products in its App Store  and its lack of participation in the Global Network Initiative , a nonprofit partnership between Google, Yahoo, Microsoft, and a number of human-rights groups and other organizations advocating for free expression online.
Failing to correct controversial words “isn’t censorship outright,” she said, “but it is annoying, and it’s denying choice to customers.”
That is, frankly, nonsense. Autocorrect is a proactive service, and one glance at a site like Damn You Autocorrect  (or just five minutes typing on an iPhone) shows that it gets it wrong a lot of the time. Against that background, it's not censorious, so much as common sense, to ensure that words which might be even more damaging don't randomly show up where they aren't wanted. In other words, Apple has made a trade-off between the mild irritation of people who find themselves having to manually correct a tweet about "abortiom" and the potentially much greater problem of having to explain to your mother than you meant to type that your cousin "amused" you, not "aroused".