It's not really a protection thing, honestly. I'm very aware of how easy it is to defeat a watermark, I've done it just for photoshop practice.
My reasonings is solely related to branding. I produce images for the web, they must have branding attached to them. I'm a very strong advocate for creating brands. Just like Apple or Microsoft vigorously pursue branding violations, they will not allow anything to go outside of their internal mechanisms without having branding on it.
I believe the same thing. Nothing I create will be presented without branding on it. It's part of my look, my info, my style, etc... It's not something that comes off for any reason other than printing and other business benefits determined by my own needs.
It's really just as simple as that. 




