Er, well CouchDB is kind of a different animal and is very far from supporting the kind of development workflow he's doing. CouchApp is very, very cool but very different and saying that things like this have been done is kind of pointless - web apps have been written in _everything_.
I get ya - sorta. I do think we are running headlong into NoSQL 2.0, where everyone ends up writing very similar but incompatible HTTP accessible key/value stores. Seems like a waste to plow energy into writing web-based key value stores when there are already plenty of good ones.
Pageforest is a pretty thin wrapper on top of a AppEngine's BigTable implementation. It does have to add things like a user accounts, user permissions, and caching layer.
The client library (JavaScript) is also design to make it very easy to write "single-page" web apps. You basically just need to write a setDoc() and getDoc() function to persist your document as a JSON blob in storage.
etherpad was awesome! Difference here is that the app lives client-side - and uses a "generic" server implementation for user authentication, storage, and push notifications.
