Mark Goodacre has a nice little entry on the NT Gateway Webblog about "what's wrong with redaction criticism."
He also alludes to an "as yet unpublished" paper arguing that before Mark, it was Jesus who was seen as Elijah, and that JBap as Elijah was a Markan invention. Somewhat coincidentally, I'd been toying with a similar idea just last week (by "toying" I mean discussing with my wife who has no idea what I'm talking about); but I can't think of how to reconcile the general belief that Elijah would precede the Messiah with the clear attestation of Paul that Jesus was recognized as the Messiah very early. I'm not sure that Jesus can be both. Perhaps an Elijah-like figure, but his Messiah-ship (is that a word?) seems to supersede being viewed as Elijah in the same sense that Mark views JBap as such. It'll be interesting to see how Goodacre deals with this conundrum.
Update: Looking at Goodacre's CV, I'm presuming that this is either the same or a somewhat revised version of his 2002 paper to the SBL.
Update Redux: As the comments on Goodacre's blog indicate, I presumed correctly.