Mike is right about things in the US.  Whatever I write at work belongs to my employer.  I'm careful not to expose trade secrets or violate the privacy of my customers.

Article are different from fourm posts.  Copyrights may trransfer to he publisher depending upon the contract for the article.  Forum post copyrights default to the OP (Original Poster).  In news groups there is no question becase usenet groups can't be owned.  Web site forums are different because the site is owned.  The responsibility falls to the site owner but not copyrights automatically.  The site owner might be forced to remove posts due to content but the site owner does not own the post.

All this is MY understanding and I might be proved to be completly full of it.  Does not happen often.