title: $.jsonp not caching
body: <p>I'm using the third party jsonp library for jquery. In the call to it, you can set cache to true. </p>
  
  <p>However, upon checking in a HTTP sniffer, it appears that all requests are still being sent to the server.. </p>
  
  <p>This with the picasa, flickr, and youtube API. </p>
  
  <p>What could be causing this behavior? It does not appear to be browser-specific as I have tested it in multiple browsers and all behave the same (not caching). </p>
  
  <p>The URLs called don't change from one request to the other and the call looks like this: </p>
  
  <pre><code>        $.jsonp({
              url: url,
              cache: true,
              async: false,
              dataType: 'jsonp',
              data: $.extend({ url: options.dataUrl, method: lookupData.method }, fixedOptions),
              callbackParameter: "jsoncallback",
              success: function(data)
              {
                  $.extend(datasourceOptions, lookupData.onData(data));
                  getData();
              }
          });
  </code></pre>
  
  <p>The only "weird" thing about my setup is that the script that will call the .jsonp is included via a .ajax call itself.. Could that be the issue here? Sounds far fetched but...</p>
  
  <p>Thanks,
  Wesley</p>
  
  <p><strong>Edit: Ok, 3 out of the 4 have Expires headers set..</strong> </p>
  
  <p>However, the fourth does not and only has these: </p>
  
  <p>Cache-Control: private
     Vary: Accept-Encoding
     Access-Control-Allow-Origin: *
     Connection: close</p>
  
  <p>(this is flickr)</p>
  
  <p>What's going on there? </p>
  
  <p>Also, is it not possible to override the header caching directives via jquery somehow?</p>