Finally figured it out:

The backend is called "md".

Dang.

...keep up the good work.

On Thu, May 28, 2015 at 11:24 PM, Ross Donaldson <gastove@gmail.com> wrote:

> --
>
> Remember to cover the basics, that is, what you expected to happen and
> what in fact did happen.  You don't know how to make a good report?  See
>
>      http://orgmode.org/manual/Feedback.html#Feedback
>
> Your bug report will be posted to the Org-mode mailing list.
> ------------------------------------------------------------------------
>
> Hallo!
>
> Recently started encountering a very strange thing: the `markdown`
> backend no longer appears in my export dispatcher. The other four I have
> listed (html, deck, ascii, and beamer) all appear; further, I can call the
> org-md-export functions directly using M-x. They're clearly being
> loaded, and behave perfectly normally. Even if the only two backends I
> configure are markdown and html, only html will appear in the dispatcher
> as an option.
>
> Emacs  : GNU Emacs 24.5.1 (x86_64-apple-darwin13.4.0, NS
> apple-appkit-1265.21)
>  of 2015-04-10 on builder10-9.porkrind.org
> Package: Org-mode version 8.2.10 (8.2.10-41-g42228a-elpa @
> /Users/gastove/.emacs.d/elpa/org-20150525/)
>
> current state:
> ==============
> (setq
>  org-export-backends '(html markdown deck ascii beamer)
>  org-tab-first-hook '(org-hide-block-toggle-maybe
> org-src-native-tab-command-maybe
>                       org-babel-hide-result-toggle-maybe
> org-babel-header-arg-expand)
>  org-latex-classes '(("beamer" "\\documentclass[presentation]{beamer}"
>                       ("\\section{%s}" . "\\section*{%s}")
>                       ("\\subsection{%s}" . "\\subsection*{%s}")
>                       ("\\subsubsection{%s}" . "\\subsubsection*{%s}"))
>                      ("article" "\\documentclass[11pt]{article}"
>                       ("\\section{%s}" . "\\section*{%s}")
>                       ("\\subsection{%s}" . "\\subsection*{%s}")
>                       ("\\subsubsection{%s}" . "\\subsubsection*{%s}")
>                       ("\\paragraph{%s}" . "\\paragraph*{%s}")
>                       ("\\subparagraph{%s}" . "\\subparagraph*{%s}"))
>                      ("report" "\\documentclass[11pt]{report}"
> ("\\part{%s}" . "\\part*{%s}")
>                       ("\\chapter{%s}" . "\\chapter*{%s}")
> ("\\section{%s}" . "\\section*{%s}")
>                       ("\\subsection{%s}" . "\\subsection*{%s}")
>                       ("\\subsubsection{%s}" . "\\subsubsection*{%s}"))
>                      ("book" "\\documentclass[11pt]{book}" ("\\part{%s}" .
> "\\part*{%s}")
>                       ("\\chapter{%s}" . "\\chapter*{%s}")
> ("\\section{%s}" . "\\section*{%s}")
>                       ("\\subsection{%s}" . "\\subsection*{%s}")
>                       ("\\subsubsection{%s}" . "\\subsubsection*{%s}"))
>                      )
>  org-speed-command-hook '(org-speed-command-default-hook
> org-babel-speed-command-hook)
>  org-occur-hook '(org-first-headline-recenter)
>  org-metaup-hook '(org-babel-load-in-session-maybe)
>  org-html-format-drawer-function '(lambda (name contents) contents)
>  org-log-done t
>  org-latex-format-inlinetask-function 'ignore
>  org-confirm-shell-link-function 'yes-or-no-p
>  org-ascii-format-inlinetask-function 'org-ascii-format-inlinetask-default
>  org-startup-folded nil
>  org-export-with-section-numbers nil
>  org-export-with-toc nil
>  org-export-with-sub-superscripts nil
>  org-latex-format-headline-function
> 'org-latex-format-headline-default-function
>  org-todo-keyword-faces '(("TODO" . org-todo) ("DOING" . org-todo)
> ("BLOCKED" . org-warning)
>                           ("CANCELLED" . org-done) ("IMPOSSIBLE" .
> org-done)
>                           ("DONE" . org-done))
>  org-startup-indented nil
>  org-after-todo-state-change-hook '(org-clock-out-if-current)
>  org-latex-format-drawer-function '(lambda (name contents) contents)
>  org-from-is-user-regexp "\\<Ross Donaldson\\>"
>  org-src-mode-hook '(org-src-babel-configure-edit-buffer
> org-src-mode-configure-edit-buffer)
>  org-agenda-before-write-hook '(org-agenda-add-entry-text)
>  org-babel-pre-tangle-hook '(save-buffer)
>  org-mode-hook '(org-bindings (lambda nil (turn-on-auto-fill))
> text-settings
>                  #[nil "\300\301!\207" [run-hooks prelude-org-mode-hook] 2]
>                  er/add-org-mode-expansions
>                  #[nil "\300\301\302\303\304$\207"
>                    [org-add-hook change-major-mode-hook org-show-block-all
> append local] 5]
>                  #[nil "\300\301\302\303\304$\207"
>                    [org-add-hook change-major-mode-hook
> org-babel-show-result-all append local]
>                    5]
>                  org-babel-result-hide-spec org-babel-hide-all-hashes)
>  org-refile-targets '((org-agenda-files :maxlevel . 3))
>  org-ascii-format-drawer-function '(lambda (name contents width) contents)
>  org-ctrl-c-ctrl-c-hook '(org-babel-hash-at-point
> org-babel-execute-safely-maybe)
>  org-cycle-hook '(org-cycle-hide-archived-subtrees org-cycle-hide-drawers
>                   org-cycle-hide-inline-tasks org-cycle-show-empty-lines
>                   org-optimize-window-after-visibility-change)
>  org-refile-allow-creating-parent-nodes 'confirm
>  org-todo-keywords '((sequence "TODO(t)" "DOING(o)" "|" "DONE(d)")
>                      (sequence "BLOCKED(b)" "|" "UNBLOCKED (u)"
> "CANCELLED(c)" "IMPOSSIBLE(i)"))
>  org-hide-emphasis-markers t
>  org-babel-tangle-lang-exts '(("clojure" . "clj") ("python" . "py")
> ("emacs-lisp" . "el"))
>  org-confirm-elisp-link-function 'yes-or-no-p
>  org-metadown-hook '(org-babel-pop-to-session-maybe)
>  org-html-format-headline-function 'ignore
>  org-babel-load-languages '((python . t) (emacs-lisp \.t) (clojure . t))
>  org-html-format-inlinetask-function 'ignore
>  org-agenda-files '("~/Dropbox/org-docs/cotidienne.org" "~/Code/astromech/
> notes.org")
>  org-clock-out-hook '(org-clock-remove-empty-clock-drawer)
>  org-src-fontify-natively t
>  )
> Cheers,
> Ross
>