Federated Wiki Feeds is coming together. After the initial release, I found that subscribing to it with River5 left something to be desired.
First, I filtered the feeds to only show new and updated items from the last week.
Second, I added flagged as active logic. An active feed is simply any wiki that has been updated in the last week.
Third, I added support for rssCloud Server which required proactively checking wikis for updates in the background. (see Federated Wiki Feeds Logic)
This way active wikis should get checked regularly and have their updates live in the river within a minute or so.
So far things are looking good. The river is a useful way to discover things that have been written in the federated wiki ecosystem.
Ward mentioned the idea of hosting the river as a service for various communities.
Right now, I'm just hosting River5 and having it subscribe to the all feeds list 
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To provide a feed for every community, I'd probably need to do some scripting against River5 or pull davereader into the app.