Challange Coins?

My cousin told me about Saints challenge coins. I had never heard of this concept. Is it new? Or has this been around for a while, and I'm just way behind the times?

http://cgi.ebay.com/NEW-ORLEANS-SAI...2579207QQihZ016QQcategoryZ25206QQcmdZViewItem

apparently my cousin didn't just make it up. Do any of you have one of these? Or is it just a clever marketing ploy to trick people into spending money on a gimmick?

Apparently the deal is at the bar, if you slam you coin on the table, and your buddy doesn't have on to reciprocate, he buys. If he does, then you buy. Is this really a "thing"?