The pins may be ID pins but they might also serve the purpose of microphones as well.

During the Real World: Hawaii season, most of the cast would go around naked so the producers had to figure out a way for them to have mics on at all times (i.e. having a mic on 24/7 is a part of the casts' contracts). The producers made puca (sp?) shell necklaces with mics in them for the cast and said if they feel the desire to go naked to put on a necklace and that way they would still have mics on all day. The cast didn't know the necklaces had mics in them but they did. I saw this on an E! True Hollywood Story episode about Reality TV.