The ending of the Gospel of Mark is one of the most puzzling issues in New Testament scholarship. Barring the discovery of new manuscript evidence, it is probably unknowable whether the author intended it to end abruptly at 16:8 or whether he or she composed a longer ending that has since been lost. I’d like to put forward a hypothetical answer to this question, however, which ties in with one of the other big questions about Mark: namely, the messianic secret.
Many readers of Mark have been puzzled by Jesus’s insistence that no one tell anyone that he is the messiah. A cynical explanation that I find somewhat satisfying is that he’s trying to account for the fact that the historical Jesus never openly claimed to be the messiah and there were people alive at the time who remembered this.
If we turn a similar logic toward the ending of Mark, he may be trying to account for the fact that no one actually claimed Jesus had been resurrected immediately after he died — of course he was resurrected on the third day, etc., but you know how unreliable women can be…
An und für sich 
I’d like to propose an alternative, less cynical reading from a collection of essays I’ve been editing. Joanna Dewey, Elizabeth Struthers Malbon, and Werner Kelber have each proposed that the oral structure of Mark (as opposed to viewing it as a text composition) makes this ending act as the ending of a parable. The audience doesn’t fall off a cliff — they keep going, and just as the women picked up the thread of faithful discipleship after the men ran off, so the audience picks up the thread after the women run off. The piece of Dewey’s that I’d recommend for this is “Oral Methods of Structuring Narrative in Mark,” Interpretation 43.1 (1989), 32-44. (ATLAS has it in PDF.)
That is also a plausible explanation. I’m surprised there was so little response to this post, though.
Me, too! I thought there would be more. Was the citation too much? Just pose the argument and run? :)