Ideally you'd want something that would let you delete your wiki when you move. If you work on Wikia, they would keep your work, so you'd be building your own competitor. There's talk of some extra hosting space going on around here, so I'll see if any of them can look at this topic.
Yes, that would be great if I could get some hosting space here, but I also found a site called wikkii.com. Unlike Wikia, it really lets the creator do whatever he or she wishes.
Its also very decentralized. For example, each wiki it hosts requires separate membership. If I'm not mistaken, wikia has you use one account for all wikias you want to edit. Basically, each wiki is independent of wikkii and all of wikkii's other sub-sites. The only connection is that they host it - and of course the domain name. They don't really monitor content or pressure owners into decisions. If you look at their wikis, you will notice that they don't even brand their name anywhere except for on a small banner in the bottom left corner.
I'm not too worried about wikkii ''taking over'' my wiki, but hosting on NIWA is still something I would appreciate.
P.S. Here's my wiki:
http://kidicarus.wikkii.com/wiki/Main_Page . It is less than a day old which is why it is so empty. Here is an example of an established wiki on wikkii:
http://gintama.wikkii.net/wiki/Gintama_%E9%8A%80%E9%AD%82 . You can barely tell it's part of a ''wiki farm''.