So, taking into account efficiency, yes a skimmer can be too big, IMO. Usually this means that the skimmer skims very little compared to how much it costs to run. As long as you are getting plenty of skimmate, then a skimmer is not to 'big' for a tank, though it may still be a energy hog.
it seems that everyone around here recommend you go 3x or 4x or more the rated capacity. I'm using a skimmer sold for 200 gallon tanks on my 55 aquarium.
I am using a large skimmer on a small reef with no problems. (E.S.S. 600 on a 46bow) It just take me two months to get any waste in the collection cup, but no effect on corals.
J.