I've recently spent some time in a small beach community, where they set up a Facebook page for the village. It's extremely active, from lost cats, local store offerings, small-crime reports and what that new restaurant opening in 2 weeks is. It's been amazing to watch people come out of the woodwork when history questions are asked.
Since so many people are already on Facebook, it might make sense for LocalWiki to leverage this with an app, rather than hope for natural migration.
As someone who blissfully retired from Facebook years ago (for all the usual cranky reasons regularly cited on HN), I really hope Facebook doesn't come to fill this niche.
But I can see how it would be a natural Schelling point[1] for doing so.
Since so many people are already on Facebook, it might make sense for LocalWiki to leverage this with an app, rather than hope for natural migration.