"any skimming over that required to maintain low levels of organic and inorganic pollutants is overskimming. Why? Because if the water is cleared of those things that are detrimental, it is also likely to be equally cleared of things that are beneficial."
Just finished reading about this recently, so have the link close at hand - hope this adds to all our total knowledge. Eric Borneman actually suggests shutting off your skimmer for part of the day!
http://www.reefkeeping.com/issues/2004-01/eb/index.php