Fonts not validating mac
The advantage of placing fonts in the root font folder gives all users on the machine access and Office doesn’t install multiple copies on the machine for each User.You can delete all these fonts after installing Office 2008 or Office 2011.All fonts used by Mac OS X system software are placed in the System/Library/Fonts.Never touch these fonts or anything in the System folder.
However, I'm guessing that this doesn't refer to Mac TTC fonts, but True Type Collections.
This helps with the duplicate font issue, but they don’t remove all duplicates.
The following applies to Leopard, Snow Leopard & Lion users.
Something unknown is causing interference with the Type Core.
Typecore is a background application installed with Suitcase Fusion that activates/de-activates fonts when Suitcase isn't running.