No, I'm not talking about the copyright holder, I'm talking about the website owner.
For example, if someone was to post on this forum some copyright material, then sue Jon for it, he would not have any limitation of liability under the DMCA unless he has a registered agent. If the companies RightHaven was going after had a registered agent then they would be protected (granted they didn't intentionally post the copyright material themselves of course). Simple.
Sec 512 of the DMCA does absolve the OSP (i.e. website owner) of liability for copyright infringement automatically if they meet the req'ts (including a registered agent with the copyright office) under the Safe Harbor provisions. But, even if they didn't meet all of those (i.e. no registered agent, and most website owners don't have one), that doesn't mean there is no limitation of liability, it just means its not automatic protection necessarily.
The registered agent provision is there to provide a known "person/address" to send copyright infringment notices to, so an OSP can't say they never got them, or a complainer can't say they sued the OSP because they had no choice; couldn't find a way to make them know about the infringement nicely. Sooooo, in the above example of Jon/Wickedfire:
Jon may or may not have a registered agent for Wickedfire.com with the copyright office ( I don't feel like checking the official Register right now) Let's say for sake of argument, he doesn't. He could still be protected from liability if he met all the other reqs because the host of the site (in this case, Softlayer)
does have a registered agent, and thus could be contacted directly, would be able to remove infringing content, etc etc. Another example is Wordpress.com. Thousands of WP blogs out there have potentially infringing content, but none of them need to have a registered agent, because the parent company of Wordpress, Automattic, serves as the registered agent for ALL blogs hosted on their WP platform, since they are in a position to be contacted, and potentially take down infringing content. As long as there is some registered contact person somewhere in a position to remove the content (even if they aren't the ones who actually do it), the Safe Harbor provisions are typically considered met, even if the actual website owner never registered themselves.
The DMCA is, IMO, a fairly poorly written reg, with lots of loopholes, but the underlying goal of it makes sense: to provide a means by which stolen copyrighted material can be removed without having to file a lawsuit every time some blogger copypastes a few sentences somebody else wrote.