<?php

$args = array(
	'nopaging'       => true, // Bad
	'posts_per_page' => 999, // Bad
	'posts_per_page' => -1, // Bad
	'posts_per_page' => 1, // OK
	'posts_per_page' => '1', // OK
);

_query_posts( 'nopaging=true&posts_per_page=999' ); // Bad

$query_args['posts_per_page'] = -1; // Bad
$query_args['posts_per_page'] = 1; // OK
$query_args['posts_per_page'] = '1'; // OK
$query_args['posts_per_page'] = '-1'; // Bad

$query_args['my_posts_per_page'] = -1; // OK