When building a public facing website that allows visitors to post comments, link to media and/or upload media (e.g. audio, video, images) ... what should I do to protect myself legally in the case such visitors link to or upload content that they shouldn't (e.g. adult oriented media, copyrighted images and/or media owned by someone else, etc...)?

Some questions that come to mind in particular:

1. Should I allow folks to post anonymously?
2. If I make visitors agree to some kind of statement whereby they take full responsibility for what they upload, what should the copy of such a statement be?

Please provide as specific as possible steps one should take if possible.

Thanks!