Wiki proliferation

Why do so many small wikis exist? Is it just that they're easy to make? Do larger wikis forget what's so great about being small?
A dozen wikis will be represented at Wikimania. A dozen more will be watching or participating from afar. Tell us about your own project, and why and how it is different from the rest!
PeanutButterWiki was designed, on the wiki philosophy, to be the simplest WikiFarm that could possibly work. It's primarily targeted at people who want a personal wiki or one for a small group of collaborators. It's free to use and password-protected, so you won't have to deal with WikiSpam. It's already one of the WikiFarms with the most wikis, despite the fact that (at the time of this writing in late June 2005) it's less than a month old.