Lukasz (a Seattle-ite) sent me an interesting email about why he's starting his own wiki about hiking trails (Hikipedia) -- and why he spent late nights rolling his own wiki software, using Python/Zope: Hikipedia has all sorts of metadata (stuff that only applies to hiking, like the length of the hiking season at a particular trail, or the ranger station address) built right into the editing interface.

I'm reminded of Clay Shirky's old point: making something completely generalized can be limiting. (But the difference between wikis and other web apps (discussion forums, say) is that all users of a wiki share the same collective space, and content in that space endures; it never gets pushed off the page simply for being old. So having a large userbase can enrich the collective space -- all of it. Trade-offs.)