The problem I see with federated wikis is potential creation of echo chambers. Current Wikipedia is often a political tug-of-war between different ideological crowds. For instance, on Russian Wikipedia, Russian Civil War article is an infamous point of struggle between communist and monarchist sympathizers, who often have to settle at something resembling a compromise.
If both sides had their own wikis, each would have very biased interpretation of events. A person who identifies as either communist or monarchist would visit only the corresponding wiki, only seeing narrative that fits into their current world view, never being exposed to opposing opinions.
Pretty sure the original post is written in the context of a typical large US supermarket with outdoors parking lot.
There people often buy more groceries then they can carry so they go with the cart to their cars to unload them. After doing that you’re supposed to push the cart back to one of cart sheds located in the parking lot, yet many people just leave it where they unloaded it and drive away.