There seems to be a surprising amount of contention relating to whether or not you should watermark your images. Some people are adamant that yes, you absolutely need to put your stamp, so to speak, on images that you're putting out there online. Other people feel that a watermark is tacky, or that somehow it's presence cheapens the quality of the image that it has been applied to. As I have found with most things in life, context is king when it comes to watermarks.
Generally speaking, I believe that yes, you should be applying a simple and sensible watermark to your images. As most people know when it comes to the Internet, once your work is out there, it can often be a bit troublesome to know exactly where it will go from there, so I figure that you're mark may as well be going along for the ride. I tend to think of watermarks as your digital signature; whether your name, brand symbol, or your literal signature it's the final piece that you attach to your finished work.
With that said, I know that we have all seen some watermarks that clearly did not get much thought. The kind that may actually be ruining an image, the genuine eyesore-style watermark. This can be avoided by putting some intention and thought behind what your mark will be before you start putting it on your work.
See the image above? A colored watermark destroys a black and white image in the fastest way possible, definitely don't do that. A watermark should be subtle, simple, distraction-free, and in harmony with the images that you're placing it on. Inconspicuous should be at the forefront of your mind. Don't use colors, or else anytime you put it on a black and white image you just created a blob of color splash. The placement of a watermark can be either consistent across all your work or mobile as dictated by each image. In my opinion, a name or signature is both less distracting and more pleasing than a symbol or logo.
It's perfectly OK to have a watermark that people see. It's less OK to have a watermark that is the first or only thing people see. Remember, the point is to avoid distraction, you're not looking to disrupt your scene. Try lowering the opacity, remember that cursive font is not required, and keep in mind that a watermark is only accent to an already finished piece.
The image below has a simple watermark that I think works with the scene. I took the time to find a font that I thought was pleasing, made sure the opacity was low enough as not to distract, and placed in an area that I felt was appropriate for the image. Let me know in the comments what you think about watermarks. Do you think it really matters at all in a digital world? Did you spend time (and/or possibly money) in designing a mark that you feel great about?