Sorry my implicit answer was that you got all the nerds into Openstreetmap and Wikipedia, so the critical mass was not there for other stuff. Wikimapia just got a bad rep, and there really wasn't room for other services when Wikimapia did what it did good.

I mean looking at the Wikimapia for Stockholm you get the feeling it is a Russian map for the next step after managing to obliterate Ukraine. Not something mapped by locals caring about the city.