It’s not completely clear what will happen, but you can ‘deactivate’ your account using the link. Nothing is said about keeping or truly deleting your personal data, or the possibility of reactivating it.
URLS:
http://www.sharethis.com
http://sharethis.com/account/deactivate
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.