Brion-
Certainly there are people who have derided the existence of the Esperanto-language Wikipedia,
Esperanto has an estimated number of 2 million speakers. That is larger than many tribal cultures or ethnic groups which have their own language, and far greater than the proposed 10,000 speaker requirement. It is the most widely accepted artificial language. It is therefore hardly a valid comparison to Toki Pona or Klingon.
I'm all for people enjoying themselves and working on Wikipedia because of that, however, as with everything, you have to do a cost-benefit analysis. And there is certainly a cost associated with letting every pet language have its own Wikipedia.
Per enjoyment alone, we should probably set up a big-ass Wikimedia gameserver, that would certainly attract thousands of possible Wikipedia recruits. (No, I am *not* suggesting that we do so.)
Regards,
Erik