All of the putatively invisible socks I have tried failed in their essential purpose: they were not invisible. Selling such socks seems to me like advertising oneself as an expert in maritime law without having ever seen the ocean or read anything about maritime law. Then again, the attorney ethics rules restrict us in ways that normal commerce avoids.
However, the helpful clerk at Journeys, which is a street-style mall-based shoe store useful mainly for its enormous selection of Chuck Taylors, convinced me to drop $10 for six pair of these beauties. They keep your shoes safe from foot sweat without advertising to the world that you are very concerned about foot sweat. Studied nonchalance. Sprezzatura is so rarely sold at the mall.