however keep this in mind, watermarking images is great and all but im a firm beliver that it does not get work. Its cool to copyright your image with your watermark. If your client likes your work they will keep you in mind if anyone asks them about a photog. Word of mouth is still the number 1 selling feature
Purposes must be understood. "Watermarking" is not copyrighting. The images are already copyrighted. There are two reasons to put a mark on an image.
One purpose is to prevent it from being used without license. That's the use I call "watermarking," and it means laying a big, ugly, obtrusive symbol or verbiage over the image that deliberately prevents it from being fully enjoyed.
The other purpose is to identify the author of the work. This is what I call "branding," and in this case it's a signature or a logo that is sized and located in a way that it still permits the work to be fully enjoyed. Ideally, the client would want the author to be known and gets a certain amount of pleasure in being associated with that author. For instance, no one who owns a painting by a famous artist covers or cuts off the signature.
In the context of an image going on Facebook, if the photographer has established a relationship with the client such that the client gets further personal pleasure out of the association (in other words, willing to provide word of mouth), the client will be glad to allow the image to be branded.
In the Facebook universe, the use of a branded image is the "word of mouth," just as a person wears designer-branded clothing specifically to be seen wearing that brand.