We imagine a probabilistic mesh network with no centralized control made from widely available and low cost components. A user sees wiki pages received by chance over short-range radio. Should she chose to fork any of these pages, or author new ones, then they would become available to others over the same radio.
A feature of this approach is that messages travel with the stations possessing them. There is no attempt to transmit messages beyond the distance necessary to complete the chance communication.
See Wireless Mesh Networks wikipedia 
Mobile
A mobile wiki site could be constructed from a Raspberry Pi Model A and a USB stick WiFi adapter.
Various automobile or backup-battery based phone chargers provide mobile power.
A mobile could offer ad-hoc service to nearby tablets making discovered content browsable.
A sufficiently credentialed user could promote accumulated content to repeatable content by forking it to their own site in the federation. This could be via keyboard and display, via ethernet (Model B), or over ad-hoc WiFi.
Broadcast
A station could make location specific content available by broadcasting it from a Raspberry Pi in that location. This could serve menus at a food court, lecture notes in a class room, or exhibit details in a museum.
Station serving travelers could use elevated and directional antennas to serve fast moving vehicles on interstate highways.
Gateway
A station could use multiple channels and relay between them. We would expect travelers to assemble and share online the best of their travels.
A Software Defined Radio offers different power, bandwidth and range tradeoffs from that available in the 802.11 unlicensed bands. We've suggested how frequency and modulation techniques could be distributed as part of a wiki federation.
Software
A transient connection would consist of a server announcing its availability, a connected client admitting interests in the form of keywords, and the server delivering wiki pages matching those keywords until the connection is broken.
The operator of a client station could expect wiki pages to accumulate and that they would all include at least one keyword by the federated wiki search logic.
A station could be a client and server simultaneously. The same or separate keywords could be used to automatically fork pages into wikis destine to be repeated.