I have recently activated IP Throttling, this basically means if you are requesting pages too quick you will get a 503 response from the server and the page you want wont come up. The current limit is set pretty low at around one page every three seconds which should suit most normal users fine. It appears to have taken a massive load off the server regardless and stopped a chunk of the leechers out there from wasting the servers resources

I will be monitoring it to make sure its not affecting too many normal users, but if you start getting this response give me a shout and I will take a look at the settings for you.