This is a good one and actually worth a thread of its own @fillipone! It's funny because I remember discussing this at university a very long time ago. In short and abstract terms: it is a rich-get-richer scheme. The winners win more and the losers lose what the winners won more. As losers can't become winners, but winners could turn into losers, the number of winners decreases whereas the number of losers increases, meaning less winners gain from more losers, thereby shifting wealth or income further from the many to the few.

With regard to merits and Bitcointalk, the social phenomenon of a queue in front of a restaurant getting longer only because it is already long describes it quite well in my opinion. But there are a lot of nice examples to approximate the effect with analogies.