This is for the ShareThis WordPress plugin found at http://wordpress.org/extend/plugins/share-this/
In your theme’s functions.php file you’ll want to input the following code…
remove_filter( 'get_the_excerpt', 'st_remove_st_add_link', 9 ); remove_filter( 'the_excerpt', 'st_add_widget' );
This will remove the buttons from displaying on pages like the homepage, search results, category pages, etc etc. That is, assuming that your theme is coded to use the_excerpt() in template files.
If you only want to remove the buttons from say the homepage of your site, you could do something like…
if ( is_home() || is_front_page() ) {
remove_filter( 'get_the_excerpt', 'st_remove_st_add_link', 9 );
remove_filter( 'the_excerpt', 'st_add_widget' );
}