It appears to me that about 2-3 years ago firms started to manufacture the challenge coins in hordes. Even in the PX you can buy a multitude of coins. I confess I have acquired some. The coins I have EARNED mean something to me. I have my MSM and ARCOMs that have been presented to me in military formations, they are superb to wear on my uniform ; but nothing can replace the pride I feel when my chief gives me for a job well done. I know this has nada to do with RCC but since the subject came up I think that folks need to understand that challenge coins are about a job well done not about numismatic worth.
IMO, challenge coins should be distributed widely enough so that all members of a group or unit can be subject to the challenge game. If the coins are instead awarded only to those who have done something special to warrant one, any challenge at a unit gathering could be awkward and probably embarrasing if a "challenger" seems to be showing off the undeniable fact that he has a coin that few others do. Special accomplishment awards were fully separate things. I noted only a few "challenges" at off-duty social events, since it was likely that everyone in the unit would probably have a coin on their person at ( virtually ) all times. The soldiers were awfully happy with their unit coin and were satisfied they weren't typically available to outsiders who wanted one.
Disclaimer : I'm arguing us military only that is the breadth of my understanding. They're given out by the Commander or SGM.