Add widget area before primary menu items in Genesis.

functions.php

<?php

add_filter( 'genesis_nav_items', 'sws_social_icons', 10, 2 );
add_filter( 'wp_nav_menu_items', 'sws_social_icons', 10, 2 );
/**
 * Adds a widget area before primary menu items.
 *
 * @author Bill Erickson
 * @author Gary Jones
 * @link   https://gist.github.com/gists/1799174
 *
 * @param string $menu Existing menu items markup.
 * @param array  $args Menu arguments.
 *
 * @return string Amended menu items markup.
 */
function sws_social_icons( $menu, array $args ) {

	if ( 'primary' !== $args['theme_location'] )
		return $menu;

	ob_start(); 
	dynamic_sidebar( 'social-menu' );
	return ob_get_clean() . $menu;

}

I thought using ob_start(); was bad?

It's not great for performance, but if a function immediately echoes rather than returns, then there's no choice. Genesis uses it in one or two places for the same reason.