One obvious feature would be to provide geo fenced Wikipedia or news feed.

Like what is the highest rated/longest Wikipedia article in the area.

Or maybe what's the 3 top radio stations and a link to them.

There is plenty of local content that Google does not surface

These are great ideas!

Geo fenced Wikipedia exists already, as a number of apps are available which offer regional maps with localized Wikipedia additions, see for example https://wiki.openstreetmap.org/wiki/OsmAnd

I could do that. Have additional information about the area based on the perimeter.

I am saying for it to succeed as multi-user, it needs to be useful first for a single user.

Twitter was never useful for single users.

It was. Twitter used to send SMS and therefore notify others on what you're doing even without them having anything installed.

Twitter started as an internal service for existing Odeo employees, so an unfair comparison if you're talking about cold, starting a social network. Twitter didn't start cold.