To the topic: Cool.
But... Aren't here getting too many wikis? I mean, we could just put it into the space wiki, I guess there is space enough or...?
Completely right! It is just disturbing to have so many wikis. If I want information where do I have to look? this is always the question I have to ask myself.
A different wiki is just useful either for fantasythings (like star trek/wars, LOTR and so on), if you want to get more specific information to those things, or for really big topics that can not be handled in Wikipedia itself.
So the spacewiki is a good idea, but exoplanets are really just a small part of it and can be handled by the spacewiki, I think.