Our friends at AddThis have done it the right way. Just follow the direct link below to delete your account.
The link is clearly visible from the profile menu, and there are no unnecessary warnings or nag screens. Deserves to be whitelisted for sure.
URLS:
http://addthis.com
https://www.addthis.com/cancel
Please note that AccountKiller.com is not associated with the business listed on this page. AccountKiller provides easy-to-understand instructions and guides on how to cancel charges and relationships from the list of businesses on our site, we have no affiliation with these businesses.