Stephen Carlson is doubting there was an original ending to Mark’s gospel beyond Mk 16:8, and he’s equally dissatisfied with the alternative hypothesis that accepts 16:8 as a suitable suspended ending (intended provocatively), for fear of imposing a 20th-century “faddish aesthetic” on the text. He suggests that we’ve been looking at the problem the wrong way, that Mark doesn’t end too soon, but too late. 16:5-7 would have been a reasonable ending, he notes, with a reliable figure assuring that Jesus was raised and will appear to the disciples, while verse 8 undercuts the resolution with a response of fright and disobedience.
Meanwhile James McGrath maintains there was probably an original ending now lost to us, and that the gospels of John and Peter can help give an idea as to what it looked it like (see his SBL paper from last year). I heard James deliver his interesting paper in Boston (along with Stephen) but don’t think he addresses why Mark was underscoring scared and disobedient women in 16:8. That’s really the question that has to be answered to make sense of Mark’s ending — whether it was the original or not.
UPDATE: Stephen follows up, suggesting that “the dominant theme of 16:8 is not the women’s disobedience but their fright”, and “this theme of fright was meant to enhance, not undercut, the authority of the young man in white [i.e. the work of God]”. Mark wrote with the best of intentions; it just didn’t quite come out quite the way he wanted.