As a casual Wikipedian, my most frustrating project has been maintaining the anti-Semitism section in the article on Roald Dahl, one of my favorite authors as a kid. Dahl made several widely publicized anti-Semitic remarks in the 1980s, such as "there's a trait in the Jewish character that does provoke animosity.... even a stinker like Hitler didn't just pick on them for no reason." For years he insisted he was only anti-Israel. Finally, in 1990, he admitted in an interview that he was also anti-Semitic. He didn't say this in a regretful way; he spoke as though his anti-Semitism was justified. It was a striking remark, since very few public figures openly admit to anti-Semitism.
I remember reading about this interview at the time. A few months later, he died. (I thought to myself, "Good riddance.") But curiously, I stopped hearing about this final admission of his. A biography I purchased years later talked extensively about his anti-Semitism but didn't mention the interview. When the Wikipedia article on him appeared, it featured several of his notorious quotes but made no mention of the one where he admitted to being an anti-Semite. I couldn't find the quote anywhere on the Internet.
Checking the newspaper databases at my university, I found a letter to the editor by Abraham Foxman in The New York Times quoting him as having told the British newspaper The Independent, "I am certainly anti-Israel, and I have become anti-Semitic." I inserted this citation into the article, though it was questioned by some because it was an out-of-context quote from an activist trying to discredit him.
Some time later, I obtained the full text of the interview from LexisNexis. Here is the entire quote: "I'm certainly anti-Israeli and I've become anti-Semitic in as much as that you get a Jewish person in another country like England strongly supporting Zionism." That's a tad more ambiguous than the Foxman version. But I put it into the article.
Every now and then, anonymous users try to delete the information in the anti-Semitism section. Many try altering the title to "Criticisms of Israel," ignoring the fact that his attacks were specifically directed at Jews, not Israel. It seems that anytime someone gets accused of anti-Semitism, people swoop down and call it criticism of Israel, whatever the facts suggest.
But I have managed to keep the section intact, and I am gratified to see how it has influenced others. Until I dug up the Independent interview, that quote was nowhere to be found on the Internet. Now it is mentioned on various websites, all because of yours truly. It's funny the effect you can have on the world from just your computer.