My biggest concern with facial hair, neck lanyards, and ties is their potential interference with rappelling - getting caught in the rappel device and bringing progress to a halt, perhaps quite painfully. At that point you generally have to reach something sharp and start cutting. Be sure to cut the hair or lanyard (I have never rappelled wearing a necktie and I don't expect to..) and do not cut the rappel rope, which is very easy to do since it is under tension. There has been at least one fatal accident some years ago because of this, and my wife just told me of a recent incident where Santa Claus rappelled into the mall, got his beard caught, and was dangling for about half an hour before being extricated. Hanging in a harness for that long can cause problems as well - impairment of circulation with a potentially fatal outcome.

Clip on ties are pretty standard in the LEO community, for obvious reasons....