SailThru plugin hack to prevent unnecessary loading of scrips and styles.

sailthru-widget-hack.php

<?php
/**
 * Force the unregistering of SailThru widgets and dequeue unused scripts and styles.
 * If you don't have the SailThru widget on your site the plugin should not load the widget's styes and scripts.
 * @todo the SailThru plugin should be improved to only enqueue when widgets are active
 * I've submitted the fix patch:  https://github.com/sailthru/sailthru-wordpress-plugin/pull/21
 * Only use this hack if you never intend to use the SailThru widget, as it will break the Sailthru widget if you choose to activate it.
 */
add_action( 'widgets_init', function(){
	unregister_widget( 'Sailthru_Subscribe_Widget' );
	unregister_widget( 'Sailthru_Scout_Widget' );
});
add_action( 'wp_enqueue_scripts', function(){
	wp_dequeue_script( 'sailthru-subscribe-script' );
	wp_dequeue_style( 'sailthru-subscribe-widget-styles' );
}, 11);