Use cheshire for JSON de/encoding.

It looks to be a little less flexible, but it supports encoding dates
(but not decoding them, for some reason?).

clj/project.clj

(defproject lp-clj "0.0"
  :description "Playing around with Clojure"
  :dependencies [[org.clojure/clojure "1.4.0"]
                 [org.clojure/data.json "0.2.1"]
                 [compojure "1.1.5"]
                 [ring-middleware-format "0.2.4"]
                 [cheshire "5.0.1"]
                 [hiccup "1.0.2"]]
  :plugins [[lein-ring "0.8.2"]]
  :ring {:handler shame/serve}

clj/shame.clj

(ns shame
  (:use [clojure.data.json :as json :only []])
  (:use compojure.core)
  (:require [compojure.handler :as handler]
            [compojure.route :as route])
  (:use ring.middleware.stacktrace)
  (:use [ring.middleware.format-response :only [wrap-restful-response]])
  (:use [ring.middleware.format-params :only [wrap-restful-params]])
  (:require [cheshire.core :as json])
  (:use hiccup.core))
;; "backend"
(defn read-shame [filename]
  (json/read-str (slurp filename) :key-fn keyword))
  (json/decode (slurp filename) keyword))
(defn write-shame [filename shaming]
  (spit filename (json/write-str shaming)))
  (spit filename (json/encode shaming)))
;; web service