For what it's worth, I expect most applications designed for Forkolator would be separated into a web service and a front end. Despite your apparent fear of such a thing, sites from flickr to facebook already let $RANDOMs write code against their datastore.
For the reasons you cite, people who fork the web service end of things, would have strong incentives to get their changes merged in upstream. And upstream maintainers have incentives to merge them: more active developers.
Front-end forks, on the other hand, could live a long time, and stray quite far from the parent, since there is a clean interface between them and the data store.
Anyway, "This will be fun to watch" is probably enough reason to give it a shot. I'm certainly not doing it because I think it will be easy.