This is an interesting project, however, as someone who administers several wikis, both public and private I honestly wouldn't give up control of the server side to the cloud ever. The simple reason is data control. I want daily backups of my wiki data. Can I do that with this?

Similarly, where's the source?

Where's the install for private wikis, such as a company's private internal wiki?

Where's the api so I can write plugins?

Where are the plugins?

What is preventing wiki spammers?

Can I theme this for groups?

I see that groups are 'private' based on my invitations to them, but how can I be sure this isn't easily compromised?

Anyway, this looks interesting, but I don't think it can be used yet for any serious wiki work.