I think one of the most famous incidents of this is Forrest Gump, which, IIRC, made no profit. The writer made nothing.
For the record, I really worry about Peter Jackson directing The Hobbit. It has to be of a very different tone. Even with some of the problems with Jackson's presentation (and I think by the time they were doing film 3, they could have added a scouring of the Shire version to a special DVD edition) it was a labor of love. He wasn't just a guy doing a movie.
Well, speaking of tone differences. The narration was light and breezy in the hobbit. The tone itself just in the books was alot different. The narrator of the hobbit is playful, like telling a yarn about the days long ago. Even though there are battles and the like, it's more sweet spirited and positive.