I personally believe that overskimming is a crock of :pooh:.
Now that you know my opinion I think it also depends on your system, maintenance routine, etc and that everyone must decide whats right for their system.
I won't get into why I think what I do, but instead will point you to an article you can read by a well respected chemist who understand things alot better than I do.
What is Skimming? by Randy Holmes-Farley - Reefkeeping.com
My general advice as it realates to skimming.
If you keep leathers, zoanthids, xenia have a good skimmer but don't go overboard. However, I have zoanthids in my tank.
If you keep SPS and LPS skim like crazy. I have a skimmer rated for a 500 gallon tank on my 100 gallon system and run carbon on top of that 24x7 to pull out anything the skimmer leaves behind and my corals have plenty of color.
Skimming provides other benefits like aereation that help reduce PH shifts during the lights out hours also.
Hope this helps. Just my thoughts, but ultimatley I would read some of the above articles and decide for yourself.
Brandon
P.S. another method of reef keeping people are experimenting with is the zeovit system
ZEOvit.com Forum - ZEOvit you don't have to buy into the expensive supplements to understand what they are doing to accomplish such great results. Low nutrient systems produce better colors in SPS.