Everybody seems to want to write a WikiClone nowadays. New features considered are wyswig editing, better history support, written in another programming language, nicer markup.
I'm thinking of something else. A WikiClone in which everything can be changed by everyone. Not just the contents, but also the code.
Clearly, this raises the issues of trust involved to new levels. I would like to run this MetaWiki on a server, but I have to make at least some assurances against attacks.
This probably means that the server actually runs in some sandbox; it cannot contact outside computers via the network itself; it can only respond to incoming requests. It cannot access the file system; it can only use a database.
It should work a bit like a Smalltalk system; just like you can view (and change) the browser's code that you are currently using, you can edit the code that is currently serving your page. In this way, rather than having to hack your own WikiClone, you can just modify MetaWiki to suit your needs...
What about versioning difficulties, it seems like this approach would run into some real compatibility problems if people started hacking their own markup parsers and the like.
To some extent this has already been discussed on WikiWithProgrammableContent. However, much closer to what you're after are SimpleWiki's ActiveSwikiAction?(?sp?) and especially MuSwiki (I have a neat description of what MuSwiki can do, but I cannot fit it in this universe -- Fermat) --BrianEwins