You're right, a few minutes in Photoshop will get rid of almost any copyright text and you'll never stop anyone who's really intent on nicking an image. However, copyrights are a useful reminder to everyone else that you own the image and don't want it copied without permission. There are also plenty of people who won't even know how to remove a copyright and so they'll just go off and find another pic that doesn't have a watermark instead.
Something small, discreet and semi-transparent would be great, but when the pictures are as good as the quackers image then I hardly notice the copyright text anyway
