<?php

/*
 *  This function will display a pretty list of the widgets currently
 *  included by Jetpack. Note that it stops WordPress execution
 *  at this stage.
 */
add_filter( 'jetpack_widgets_to_include', 'list_jetpack_widgets' );

function list_jetpack_widgets( $widgets ) {
    ?><pre><?php print_r( $widgets ); ?></pre><?php
    exit;
}

/*
 *  This function removes the Facebook Likebox from the list of widgets
 *  that Jetpack includes.
 */
add_filter( 'jetpack_widgets_to_include', 'filter_jetpack_widgets' );

function filter_jetpack_widgets( $widgets ) {
    if ( ! is_array( $widgets ) )
        return;

    $filtered_widgets = array();

    foreach ( $widgets as $widget ) {
        if ( stristr( $widget, 'facebook-likebox.php' ) )
            continue;

        $filtered_widgets[] = $widget;
    }

    return $filtered_widgets;
}