There are several reasons why you should take care in holding and protecting your visual copyright. For starters, many of the images you take during a wedding are free from the context of the specific wedding party itself: details of flowers, rings, churches, unidentifiable children being themselves, a bouquet flying through the air (you get the point).
Now imagine if your perfectly timed, composed and exposed picture ends up on a commercial greeting card 3 years from now? The greeting card company is an international one and your image has been used for a card distribution of 5 million pieces selling at an average $3 a piece.
You might not believe it right now, but you will undoubtedly take at least one such image at every wedding you cover, whether you intend to or not.
Do you remember how you ruined your new suit got while trying to get that picture??
Before you hand anything over to the client, before you upload any images into the internet ether, before you send anyone your know that cool wedding shot by email, BULK register ALL of the wedding images you took at the U.S. copyright office. A bulk registration costs only $35. In other words, for only $35 you can register all of those wedding images you took (but not yet published on the internet or elsewhere) using ONE single bulk registration form.
In the long-term this registration "insurance" will pay off handsomely. Sooner or later some person or company will use your best images in an unauthorized way. It's only a matter of time before this infringement happens.
Happy shooting!
Kevin