Thanks for all the good replies, it is greatly appreciated.
I just spoke with a supporter from my hosting company, he refused to install anything to prevent this from happenening again. While I argued that anyone could hotlink my images and seriously run my bandwidth bill in the air, he claimed that hotlinking is never using more than 5 GB at most per month.
He wouldn't even spend 5 seconds creating a .htaccess that would stop all of this. I really hate to stick with this lousy host, but they're the only host I know that will charge solely on (a variable) traffic usage.
Example: I used 75 GB in December and paid 75 x $1.1 the 1st January. Let me know if you can offer a similar deal, I have a few domains I'd like to move...
------------------
TopBucks: $35-$40 per initial signup. $250 startup bonus!