Actually, most of the people in this thread have it slightly wrong.
1- To be protected by the Safe Harbor provisions of the DMCA you MUST register your site and agent with the copyright office. Here is a link to the form, and a link to some of the listings.
http://copyright.gov/onlinesp/agent.pdf
DMCA Agents - Index A | U.S. Copyright Office
2- If you are not registered at the Copyright office you simply can't hide behind the DMCA.
Many may not know that, many might think I'm wrong, but no matter - its true and it means that you can be sued if you displayed some persons photo(s) or video(s) without permission.
Those that have been around a while might remember the Liberty Media v Oron case. That issue came up in that case and Oron had to pay - and in fact it put Oron out of business.
Here is a good article about that issue written just last month.
Getting DMCA Safe Harbor Right - Plagiarism Today