couchdb has filtered replication so you can selectively choose what gets replicated

and it has continous replication with a comet changes feed, so push notifications are also built in.

the data schematics are a bit of a non issue, at some point someone needs to agree with what the data format is.

basically couchdb already has a lot of this functionality baked in as first class citizens, I agree that there is a lot of situations where people will be hammering couch into a hole that doesnt fit (source control would be a good one), but I certainly dont think this is one of them.