get_most_recent_post_of_user

 * properties of the network being viewed.
 *
 * @see wpmu_current_site()
 *
 * @since MU (3.0.0)
 *
 * @global WP_Network $current_site
 *
 * @return WP_Network
 */
function get_current_site() {
	global $current_site;
	return $current_site;
}

/**
 * Get a user's most recent post.
 *
 * Walks through each of a user's blogs to find the post with
 * the most recent post_date_gmt.
 *
 * @since MU (3.0.0)
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param int $user_id
 * @return array Contains the blog_id, post_id, post_date_gmt, and post_gmt_ts
 */
function get_most_recent_post_of_user( $user_id ) {
	global $wpdb;

	$user_blogs       = get_blogs_of_user( (int) $user_id );
	$most_recent_post = array();