People do incredible things that are fun to do, and they will do them for free. That's why most dayjobs are boring. Because the fun part is being done by volunteers -- for free. When designing anything, consider the fun factor: Who will have fun using it? Because those people will be using it all the time.
When you are writing a new WikiEngine, it better enable the founders using your engine to do fun things. Wiki engine must allow founders to tinker with the software. Because doing it is fun. By providing a community where extensions and patches can be posted, even when they are not included into the software, you are increasing the fun factor even more.
This is a contradiction to the HumaneInterface book by JefRaskin. He says that if the software has options, that usually is a sign that the designers did not do their job. If they had done their job, they would have choosen the better design and eliminate the option. What he doesn't see is that some people don't just use an editor to write texts. They enjoy tinkering with the software.
This is also why it is hard to maintain your FeatureKarma, because people will enjoy even useless options and customizations. On the EmacsWiki:EmacsChannel there is a bot called fsbot. This bot knows all the pages from the EmacsWiki plus lots more. It also knows countries, quotes, fortune cookies, jokes from the Emacs distribution such as running a variant of Eliza. It is amazing to see how much time people will devote to playing with fsbot. The fun factor makes fsbot a popular bot. And since it is popular, it is being fed with more useful information by users. The other bots on the channel are practically not fed at all.