Who owns the content of a post posted on your forum? How do you respond if someone demands “their” posts be deleted and they threaten legal action if you don’t, but removal of the posts ruins a valuable thread? Where do you as the forum Admin or owner stand?
By default in the non-forum world, authors own the copyright on their own creations. This is an automatic right of the creator of the work, so technically the creator of the post is the copyright owner. However, by posting on a forum, you would have accepted the terms and conditions when you join a forum that covers this type of publication and what it implies. In posting you are accepting that your creative content (ie your post) will be published by the forum administrator and owner, and also that they have the right to edit or do what ever they like with your post as they see fit.
But does that mean that when material is publicly posted in a forum that this implies transfer of copyright ownership? The copyright lawyers can not even agree on this. The reality of the matter seems to be that there is no clear legal precedent yet made on this matter, and therefore until there is, then the issue will remain vague and uncertain. It has never been tested in court, let alone the issue of legal jurisdiction as to country of the Administrator, the country of the servers the forum is hosted in, etc.
What appears to be important is the terms that members agree to when they joined and whether they can withdraw the material they posted if they want to (eg when they leave a forum). To cover yourself, add into the forum rules something to the effect that ‘copyright to forum posts and other information become the property of the forum‘. In my forum rules I have strictly pointed out that all posts become owned by the forum. This gets politely pointed out to those making threats. I never hear from them again.