Whenever the topic of editing sf comes up, I think of Frank Herbert. Dune is a great book, in part because of all the stuff that (I have heard it said that) John Campbell made him take out of the body of the book and stuff into the appendices where it belongs. (Cf. LotR.) And after its success, FH said, Hey, I'm a great author, I don't need no steenking editors! And look at how they ramble on and on and on and on and ... Worse with each sequel.
-thnidu, commenting in skzbrust's journal. (link)

Had to quote this here because it's just so painfully accurate. I picked up Dune when I was 15, and loved it. Went though Dune Messiah and Children of Dune in short order. (Children is still my favorite of them all) Then came God Emporer of Dune, and I started to wonder if the man wasn't taking too many hits of something mind altering. After stubbornly wading though the last two books, I was convinced of it. The sheer overwrought-ness of Heretics of Dune and Chapterhouse: Dune killed any interest I might have had in the continuation novels. (Though I've heard that they don't actually suck)

Herbert's not alone here - plenty of authors commit the sin of believing that they've "outgrown" the need for editors. (Hey, over in the corner! I'm looking at you, Ann.) It seems to be a professional hazard.