You are obviously focusing on the presentation-layer (mediawiki) and completely ignoring the data store that everyone else is quite psyched about.

Here is what scalaris provides: distributed, fault-tolerant, replicated key-value store (a la Dynamo/SimpleDB.) This layer can be smeared out across hundreds or even thousands of nodes, it can provide data consistency across the replicas (via Paxos, something that SimpleDB/Dynamo cannot provide and pass back to the application layer for reconciliation) and it can do this rather quickly.

That is a rather powerful component to make readily available to any Erlang app. If you can't think of ten or twenty possible applications of this then you are not trying hard enough.