From Dale Allison, "The Historians Jesus and the Church", Beverly Roberts Gaventa and Richard B. Hays, Seeking the Identity of Jesus: A Pilgrimage (Grand Rapids: Eerdmans, 2008), 79-95 (81):
"None of what has been said gives us good reason to attribute Mark 9.43-48 to someone other than Jesus, and my own strong inclination has always been that the verses go back to him. But if I am candid, I am not really sure what arguments or criteria I might muster to persuade others who are inclined to a different opinion or even no opinion at all. I can say that the language is vivid and shocking. My mind's eye beholds a bloody stump and an empty eye socket when it encounters these words, from which it follows that if Jesus did say something like Mark 9.43-48, it would stick in the memory. But this begs the question: Did he really say something like it?"
Incidentally, the article is fantastic, and I would like to blog about it in due course, but I thought I would note this incorrect usage of "beg the question" since the topic has been raised today.