disable-full-size-image.php

<?php
/*
Plugin Name: Disable Full Size Image
Description: This plugin removes the "Original Size" option in the drop down when inserting an image into a post
Version: 0.1
Author: Bernhard Kau
Author URI: http://kau-boys.de
*/

function disable_full_size_image( $image_size_names ) {
	unset( $image_size_names['full'] );
	return $image_size_names;
}

add_filter( 'image_size_names_choose', 'disable_full_size_image' );