So here are your take away points: A photographer will own all rights to an image taken unless (1) the photographer assigns, licenses, or otherwise transfers rights to someone else (you'll know if you've done that because you have to reach an agreement with someone); or (2) the image is considered a work made for hire, in which case the hiring party owns it.
A photograph will be considered a work made for hire in one of two ways. The first way is if it was taken in the course of employment (for example, an image of Barack Obama taken by an employee of the Associated Press). The second way -- and you must meet all three of these conditions -- is that the photographer was commissioned, signed a written agreement acknowledging the photos are works-made-for-hire, and (perhaps most importantly) the job assignment falls within one of a few specific categories listed in copyright law.
Since most wedding photographers are not employees and don't use written work-made-for-hire agreements -- and since it's questionable whether wedding photos will fall within the enumerated categories listed in the law -- wedding photographs are, as a general rule, not likely to be works made for hire. One caveat: Our helpful staff uncovered this article which points out that if you operate your photography business as a corporation or LLC, you will be an employee of that corporation, and your copyright registration must reflect that status.