If you want to unblock Google and Yahoo in your hotlink protection, add this to it:
RewriteCond %{HTTP_REFERER} !^
http://([a-z0-9-]+\.)*yahoo\.com(:[0-9]+)?($|/) [NC]
RewriteCond %{HTTP_REFERER} !^
http://([a-z0-9-]+\.)*google\.([a-z]{2,3}|[a-z]{2}\.[a-z]{2})(:[0-9]+)?($|/) [NC]
Yahoo only uses .com for all country specific portals they have.
Google has all kinds of TLD's, but it will cover: 2-3 char TLD's (ca,com,net,se,dk.....) and the ones that has co.uk, co.jp for example. So theoretically it would let through a fusker site that was on a 2 char domain like as.ca, but I doubt that will ever exist
