Tweetie 1.3 rejected from App Store because of swearing on Twitter
Most of the competing iPhone Twitter apps also have trends, and would have been just as "offensive" if they had run into the bad luck of being tested while something Apple didn't like was popular. The Atebits Twitter account has been equal parts frustrated and practical in commenting on the rejection. I think the idea of sending screenshots of trends in other Twitter apps to Apple, hashtag cussing included, is brilliant.
Update: Tweetie 1.3 has now been accepted into the app store, and the developers don't seem to have any hard feelings toward Apple. I hope this case highlights the need to continue improving the app store submission process.