Relevant to me because the other day I had a couple of convention photos that showed up online with my watermark removed. Grrrrr.
I'm fine with people using my con photos for fanart. For this reason I keep my watermark small and tucked away in a corner. What I don't like is people removing that watermark and then re-posting the photos as if they were their own. If you're going to post the photos, just keep the watermarks where they are.