but, a watermark can mean the difference between you having the claim on an image and some one taking it from the web for their own profit. Which is done by unscrupulous people EVERY day!
Yes, it may seem elitist, but it is the same reasoning behind kids putting their name on their paper in school. This is your work, good quality, mediocre or just plain bad, and no one else should be able to take your work and use it to their own advantage.
Plus, if you do make nice images and people want to have them for their own and take them off the web, don't you want to let the world know that you are the creator of that work.
If I was a forum crawler out there looking for images for my firm, and there are people who do just that, I'd follow your link and grab every image, just because I know that you have no watermark/copywrite, which means you defacto gave up your right to that image when you posted it to general viewing on the web. Even at the lowest cost for copywrite free imaging, a firm can rack up a few dollars when purchasing images, finding them for free helps the bottom line and you are essentially giving away the farm for free when you don't at least watermark your images.
In the long run, you cut the legs off of people who make their living off their imaging, by giving it away for free, either by choice or by neglect to protect your own imaging.