If you are using the Social Bookmarking service directly from AddThis, you may notice that your URLs are sometimes appended with a strange (3) hashtag and a series of numbers/letters at the end.
For example, instead of:
http://yourstoredomain/product_p_01.html
the URL will appear in some areas as
http://yourstoredomain/product_p_01.html#.UvT5cDlcQRs
This is a result of using AddThis' "address bar tracking" function, which is used by AddThis for basic analytics.
Please review AddThis' article (located here) on removing the function, so the hashtags are not present.