Add This slows page loading and the solution

The solution is to load AddThis script in asynchronous mode. This would prevent AddThis from loading other assets except the initial script. After loading this initial script your website will break connection with the AddThis server and load itself further. When your website’s DOM has fully loaded, you can call the init() function of AddThis to resume loading of AddThis assets.
To do this, just add the following parameters to your script call
async=1&domready=1
So, instead of the following code:

1	<script type="text/javascript" src="http://s7.addthis.com/js/250/addthis_widget.js#pubid=xa-4f3e33c72b9a4e40"></script>

Use this one (change the pubid parameter to your pubid):

1	<script type="text/javascript" src="http://s7.addthis.com/js/250/addthis_widget.js#pubid=xa-4f3e33c72b9a4e40&async=1&&domready=1"></script>

And then call the init() function right before closing the body tag

1	<!-- Call for AddThis init() function -->

2

<script>

3	function initAddThis()

4

{

5	addthis.init()

6

}

7	initAddThis();

8

</script>

You’ll see that your AddThis widget is loading faster than before. Of course there could be other reasons that might be slowing down your website. You should look at them separately.

ref:
http://techwelkin.com/slow-addthis-reason-and-solution#.Ui7RjaydnLY