I use a watermark mostly to differentiate between my photography shots and just fun, spur of the moment shots; haha, and I like to think it offers some protection. Basically, I'll have three copies of the picture: the original, an edited version, then the edited version with a watermark.

Everything that gets posted here is without the watermark because I know that some people find it annoying when critiquing the photo. I don't really have a "design," just the copyright sign followed by my name. That's about it. I also try not to make it huge (it usually ends up distracting me ). And I've never asked people what they think of it since it isn't fancy or anything of the sort.

I've heard you can put like an invisible code on the pictures so that if someone steals it, you can prove it's yours. If I knew how to do that, I probably wouldn't use a watermark (not that any of mine are worth stealing ... yet ).