Which wiki farm should I use for my writing project?

OK, so I have an interesting idea for a writing project that's a bit experimental, but it requires a wiki. What kind of project? I'll tell you some time after I get started or I give up on it. The problem is that I don't know much about which place to get a wiki from. I don't know how different wikifarms differ from one another, or even if they differ from one another in any meaningful way. also, reading the NIWA Manifesto has left me rather worried about my choice. I am interested in free hosting at the moment, but plan to get my own website if I can prove to myself that I won't give up on this and that I can get enough money from it to cover the hosting costs. And the nature of my project will require the ability to lock part/all of a page from being edited.

So free hosting, few barriers to moving to another site, and being able to lock pages are my main concerns.
Any advice?

I'm currently using Wikidot.com for a private wiki for collecting my own personal thoughts. It's entirely free and allows you to create an unlimited number of pages. You can choose to make your wiki private or public, and I do believe they allow locking pages. It's fairly easy to format. I don't know how easy it'll be to move. You might just have to copy and paste all the pages individually into the new website.

Another option could be wikia.com. It's also free, and I think it's a little easier to use. You can also lock pages. I simply don't like to use it because I don't think you can make them private, but it's great if you want to invite people to join.

Thank you. I guess my worrying about why groups like NIWA would avoid wikifarms might have been misplaced if no one has brought it up yet.

I am not interested in whether it can be set to "private" or not and my idea would really benefit if there are any wikifarms that offer the ability to lock only part of a page. Like being able to have all but the top section of the page editable by anyone and have only the admin able to edit that top section. But I suppose that a mix of locked and unlocked pages will do until the eventual switch to self hosting.

I had huge concerns about rights issues with regards to wiki farms, so I opted to set up my own Wikimedia-run wiki on a paid server (a so-called "web hotel"). It's very easy to set up and get running, but it gets complex really fast if you want to do anything even slightly unusual, such as enabling images. So that might be one reason to go for a farm, if all te options are enabled already

Including domain name, I pay 450 DKK pr year, and the web hotel is able to host multiple sites (I get many GB of server space), so if I wanted to host 3 sites instead of one I'd be paying 650 DKK per year, or a bit over $100.

Also, whatever you decide, use Media Wiki, the "software" that Wikipeia runs on. I've seen wikis running on other kinds of software and they're not pretty. Just something as basic as visible and clickable categories. I think it might be Wiki Dot that hasn't got those: Unregistered users can't *see* the freakin' categories.

On Media Wiki, you can do that by having the page include a locked template, and put the opening section on the template.