Here's an interesting article about creatively watermarking your photographs. Would you like to see someone try to scrub these out of the photo?
Farbspiel: Creative Watermarking – How to Integrate Your Signature into Your Photos
If you want to apply a watermark / signature to your images, do not simply paste a huge piece of ugly text over it. This will deter viewers.
If you are willing to invest a bit more time, you can produce a signature that seamlessly blends into the image, tagging it as being yours without turning off viewers.