I have a number of photographer friends, some professionals and others amateurs. We share our images online with Facebook and via our personal web sites. Something I've noticed, and this seems to be occurring primarily with my amateur friends is a tendency to watermark their images with a logo or studio name. Some photographers wrongly believe that by placing their mark on their image, that image now enjoys some level of copyright protection it otherwise may not have. Not true. Your image is copyrighted just the same with or without the mark. What makes a difference is rather or not they've registered that image with the library of congress copyright office.
At first glance, it seems to make some sense. Protecting your images from unauthorized duplication or theft, advertise yourself. Those sort of things come to mind and the application seems to follow trends amongst common circles.
Here's what I've also noticed. Most of my professional colleagues and friends are very frugal with their watermarks if they use them at all. Most commonly, printed proofs are clearly marked so that customers can see the image but be dissuaded from making photo copies. This protects revenue generating images from being absconded with. I also see them do it with final product prints, a makers mark. Standard business practice. I've received customers from those makers marks on photographs I've sold. People who saw the photo and contacted me. Usually, the makers marks are on the back side of the print or perhaps a small but readable logo on the lower corner of the print. What I never see though, is a professional interfere with the artistic esthetics of the image by superimposing their logo or name. It's kept elegant and unobtrusive.
I don't put watermarks on images I post on the internet unless they are images that are of high enough resolution to be made into a decent print or I'm putting them in a customers gallery and offering them for sale. Simple display quality images don't need a watermark if you aren't trying to sell it to the people you're showing it to. The makers mark or watermark is there to keep your paying customer honest. Another reason is that all of my revenue generating images are registered with the copyright office, so if somebody wants to use it without permission they run the risk of having to pay statutory damages, which can get pretty expensive. It's like buying a lotto ticket. I constantly police this and there's a part of me just waiting for somebody to steal one of my shots and use without my knowledge. It's never happened.
So, think about why you are putting a watermark on your image. Is it to protect a sale or is it an act of vanity? Personally, I think it's mostly vanity and I think it mostly detracts from the image.
Just my opinion, but I'm sticking to it.