Populate WordPress User Meta so that even users who have never logged in will display on the Members BP page

ab-bp-retroactiveusers.php

<?php
/*
Plugin Name: Retroactive BP User Acticity
Plugin URI: https://gist.github.com/3953927
Description: Makes all BuddyPress users visible immediately on user creation and retroactively adjust users to allow for their display before logging in.
Author: Aaron Brazell
Version: 1.0
Author URI: http://technosailor.com
License: MIT
License URI: http://opensource.org/licenses/MIT
*/

/**
 * A BuddyPress class for user creation simplicity
 *
 * @author Aaron Brazell <aaron@technosailor.com>
 * @package ab-bp-prepopulate-users
 */
class BP_Prepopulate_Users {

	// MySQL default limit is 1000, but you might have more users, so modify this value accordingly.
	const USERS_NUMBER = 1000;
	
	/**
	 * PHP constructor method. Requires PHP 5.2+
	 *
	 * @author Aaron Brazell <aaron@technosailor.com>
	 * @package ab-bp-prepopulate-users
	 */
	public function __construct() {
		$this->hooks();
	}

	/**
	 * Method to tie methods in this class into the WordPress hook system
	 *
	 * @author Aaron Brazell <aaron@technosailor.com>
	 * @package ab-bp-prepopulate-users
	 * @return void
	 */
	public function hooks() {
		// Fix existing users. Will only ever be run once
		add_action( 'wp_loaded', array( $this, 'retroactive_user_fix' ) );

		// New users get the last_active meta
		add_action( 'user_register', array( $this, 'user_active_on_create' ) );
	}

	/**
	 * A method for retroactively loading existing users with the last_active meta_key. BuddyPress will not show
	 * users who have never logged in so this is a quick fix to get around that problem. Method stores the abbp_retroactive
	 * option in the WordPress options table after it is run once on page load. After that, the method short circuits
	 * if the option exists, preventing unnecessary database queries in the future.
	 *
	 * @author Aaron Brazell <aaron@technosailor.com>
	 * @package ab-bp-prepopulate-users
	 * @return void
	 */
	public function retroactive_user_fix() {
		if( get_option( 'abbp_retroactive' ) ) {
			return;
		}

		$users = get_users( array(
			'fields' => 'ID',
			'number' => BP_Prepopulate_Users::USERS_NUMBER
		) );

		foreach( $users as $user_id ) {
			// Check to see if the user has activity
			if ( bp_get_user_last_activity( $user_id ) ) {
				continue;
			}
			
			// Inactive so lets activate
			bp_update_user_last_activity( $user_id, bp_core_current_time() );
		}
		
		// Clean transient cache
		delete_transient( 'bp_active_member_count' );
				   
		// Only do this once so not to tax the database unnecessarily
		add_option( 'abbp_retroactive', true );
	}

	/**
	 * A method for pre-populating the last_active meta_key in the usermeta table. BuddyPress only displays users with
	 * this key so we force the user to have that key to get around the limitation. Hooks on the user_register hook.
	 *
	 * @author Aaron Brazell <aaron@technosailor.com>
	 * @package ab-bp-prepopulate-users
	 * @return void
	 */
	public function user_active_on_create( $user_id ) {
		bp_update_user_last_activity( $user_id, bp_core_current_time() );
		
		// Clean transient cache, just in case
		delete_transient( 'bp_active_member_count' );
	}
}

new BP_Prepopulate_Users;

Superb, thanks so much.