You’ve likely heard of Murphy’s Law (that’s Sod’s Law, you UK lot): anything that can go wrong will. But did you know there’s an editorial version, too? Muphry’s Law is the “principle that any criticism of the speech or writing of others will itself contain at least one error of usage or spelling.” (See this About.com article for the etymology and some fun examples.)
I’m all too aware of this phenomenon. That’s why I instituted the “My Bad!” contest. If you spot an error anywhere on my site, I’ll reward your eagle eye with a $5 discount off your next project. ALL writers–even (especially?) editors–need editors.