I don't watermark my images. I usually upload at 1024 res max. IMO its pretty pretentious to watermark images as a hobbyist photographer Kind of like those people who buy a canon rebel or a nikon d40 and get the idea that they are now a pro, and open up a photography business.

Who cares if someone wants your images on their desktop wallpaper? Its one more person appreciating something you made. So long as someone isn't using your image to make themselves money, it isn't worth it.