As mentioned in many other threads, i have been planning on changing the way hotlink protection works for paid users.
If you choose to enable this feature you will only be able to hotlink (fullsize images) to the sites that you specify as allowed.
Previously you had to block sites, the new approach makes more sense as its not easy to find out what sites you need to block.
I will be disabling the old system and deleting everyones blocked domains, you will then need to login and choose what sites you wish to allow then enable the feature again.
Everyone with a paid account will recieve an email about this change shortly.