add_filter( 'sidebars_widgets', 'wpse17681_sidebars_widgets' );

function wpse17681_sidebars_widgets( $sidebars_widgets ) {
    if ( !is_admin() ) {

        foreach ( $sidebars_widgets as $sidebar_id => &$widgets ) {

            foreach ( $widgets as $idx => $widget_id ) {

                if($sidebar_id == 'sidebar-1' && $widget_id == 'text-3' && !wp_fusion()->user->has_tag('Tag Name'))
                    unset( $widgets[$idx] );

            }

        }
    }

    return $sidebars_widgets;
}