To be honest I have never heard of a challenge coin before so I'm not privy to their use other than what was posted in the thread.
I don't recall mention of a medal, t-shirt or bumper sticker. No gaudy, over the top "look at me" bs.
The original thought was strictly for a discreet little symbol of recognition.
At a glance we can all see that zulu served (and we thank you for your service)
I thought it would be nice to know at a glance who has/had contributed above and beyond to the firearms community...and most importantly, how many drinks in a round
...thinking about it now I see it as a positive way to entice members to earn one. As an ongoing thing it may motivate members/new members to give back to the firearms community where they may not have. A thread they may/may not see isn't much of catalyst for contributing. A symbol that makes them curious to know more (and if possible takes them to the thread if clicked) could go a long way to adding contributors on a grander scale. Who knows what motivates people to go above and beyond? Look at all the folks out playing pokyman...