US Soccer has recenlty issued new guidlines for use of headsets. These guidelines can be found here (US Soccer Memo on Headset Usage). Bascially, unless the entire crew consists of regional referees or the competion authoirty (league or tournament organizer) approves thier use, headsets are not to be used in USSF sanctioned games.
That being said, CASRA supports the use of headsets in all instances where you are permitted to use them. The following presentation is meant to give referees an overview of best practices when using communication systems. It is very important that if you use communication systems, you must have an extensive pre-game discussiuon about the topics contained in this presentation.