I can understand the reason behind watermarking your pictures to a certain extent - but there is a right and a wrong way to do it. Allow me to illustrate.
Many photographers add a big freaking watermark across the whole photo. Like so.
It doesn't matter what level of transparency you're using. You might as well make it big, black and bold because you can't see what is going on in the image!
You might as well use this:
Because that's pretty much all the viewer gets anyway.
Are there acceptable ways of putting a watermark on your photos? Sure!
Continuing with my example, here's something that's at least bearable:
Of course - you can also make yourself a pretty little logo and use that instead.
image courtesy of Jenn Hilderbrand
Jenn uses a cute J and H for her logo and she sticks it somewhere unobtrusive.
Do I like it? Nope. Can I live with it? Absolutely.
On to a more famous example: Douglas Sonders
image courtesy of douglassonders.wordpress.com
Again: Do I like it? Definitely not. Can I live with it? Sure.
When you boil it all down, watermarks are ugly. They get in the way of the image. So why would anyone ever watermark their photos? Security? To show ownership?
Anyone with even the most basic skills in Photoshop or Gimp can remove any but the most heinous watermark. If it takes up the whole photo (like the examples at top), then nobody can see the image and it isn't worth stealing to begin with.
So, we find ourselves in a bit of a pickle. Watermarks that allow the viewer to see the photo detract from the image and are easily removed. As such, they work poorly to show ownership or to provide security. While huge watermarks provide security and proof of ownership - nobody wants to steal your image because it looks like shit.
What's the solution? How can you make your images pretty and safe at the same time?
It depends on what you're afraid of. If you think your photos are going to get stolen and printed, all you have to do is resize them to 72dpi at say, 600 pixels or smaller at the widest. Nobody can print that and make it look good. Problem solved
If you're afraid of someone stealing your images and using them on the internet - this won't help. You can, however, embed metadata that shows YOU own the photo! That way, when some asshole steals it and puts it on his website, you can say "Hey, you've got my photo without my permission. Pay me $1000, or remove it or I'll take you to court." If you do go to court, you can download the image off the asshole's website and pull up the metadata that proves you own the photo.
You also have to be careful about specifically which actions are protected under copyright. I can steal Jenn's and Douglas's photos for use here because I'm using them in a form of critique and as educational examples. Totally legal. If I was printing them and putting them on billboards - not so much.
Whew. A fairly long post for me. What do you think about watermarks? If you use them, why? What did I miss?
As always, comments are appreciated.