The Internet world is growing, and there are limited ways for YOU as an artist to protect your work, especially when there is no way to know who, or what you are protecting it from. One social networking site has it in their terms of service agreement that once a photo is uploaded, they are free to use it for whatever means they wish.
That is fine - I agreed to those terms of service, but I will still make it a little more difficult for them. If I have a larger, prominent watermark, they will have to pay their graphic designer to work longer on removing it. I would imagine that in that case, they would just opt out for someone else's photo.
I still aim to make a mostly transparent watermark that is easily viewable, and although a little distracting at times, will not interfere with what I feel the main subject of my photo is. - I would never put my watermark across a model's face in a portrait photo.
The times are changing, and it is up to everyone to do what they feel necessary to protect their own work in these times because no one else will do it for you.
How do you feel about this? Similarly, what do you do to protect your own work, or do you not bother at all?