How to remove your ShareThis account
It’s not completely clear what will happen, but you can ‘deactivate’ your account using the link. Nothing is said about keeping or truly removing your personal data, or the possibility of reactivating it.
Direct removal link: http://sharethis.com/account/deactivate
Helpful Trick: Removing online data
Helpful Trick: Remove third-party logins
If you signed up for ShareThis using a third-party login such as Facebook or Twitter, you probably want to revoke all access from ShareThis. Click here to find out how.