We noticed that Disqus was causing our Tumblr blog to load slowly. This was the fix:

$(function(){
  var links = $('a');
  var query = '?';
  for(var i = 0; i = 0) {
        query += 'url' + i + '=' + encodeURIComponent(links[i].href) + '&';
    }
  }
  $('head').append('<script charset="utf-8" type="text/javascript" src="http://disqus.com/forums/{text:Disqus Shortname}/get_num_replies.js' + query + '">' + '</script>');
});

—Sam Saccone