I was searching for an answer to this, but found it on Add this support page, and in case the difficulty hasn't been resolved or anyone who needs a reply, the solution is as appended:

At your tpl_product_info_display.php or whichever page you have added the 'add this' code, change the addthis_config.data_track_addressbar = true; to addthis_config.data_track_addressbar = false;

Sample code:
<script type="text/javascript">
var addthis_config = addthis_config||{};
addthis_config.data_track_addressbar = false;
</script>

More information about address bar sharing analytics is available here: http://www.addthis.com/help/address-...ring-analytics