Though the comments here so far seem positive, there has also been a lot of negative backlash, primarily out of privacy concerns.
Elliot Murphy posted a comment on LWN clarifying his message (comment here: http://lwn.net/Articles/356947/ attached to parent http://lwn.net/Articles/356911/). The most relevant part is this: "It seems I was overenthusiastic when sending that email to the couchdb dev list, and left out an important word: 'can' be replicated :)"
In other words, this is an optional service that you can choose to use -- no default install is going to send your info to Canonical.
clearly Ubuntu think CouchDB will be useful in other areas... and this is a trial run.
Id stick my neck out to say that something like CouchDB will become the de-facto standard for almost all data. Data that isn't {securely} on the web is in effect data that doesn't exist, while more data than not is naturally in a graph or tree-like form.
Mix in offline mode, JavaScript on client and server and you have a really nice development stack to make apps with.
I can imagine a generation of teenagers developing web apps [they'll think there is no other kind of app] using map / reduce idioms to get to their data, SQL a thing of the past.
Would be nice but my feeling is that the simplicity of SQL CRUD statements could be grokked by way more teenagers in the "past" than will be able to grasp map-reduce in the "future".
Myself I'm also into document DBs and graph DBs, a lot. But for the kind of rapid prototyping that got most of us going as teenagers in the first place, I'd argue table based data with the simplest incarnations of INSERT UPDATE DELETE SELECT WHERE haven't been beaten yet by those no-SQL DBs.
Is it possible to replicate a users' local database into a shared "cloud" database (many-to-one) or does the "cloud" have to have one database per user (one-to-one)
CouchDB's current built in replication doesn't have the concept of sharing partial data yet. It currently push/pulls everything in a single Database. Conversely it's also a trivial thing to create a new database, so one database per user would certainly be possible. Also as the project develops that is functionality that is intended to be there.
Elliot Murphy posted a comment on LWN clarifying his message (comment here: http://lwn.net/Articles/356947/ attached to parent http://lwn.net/Articles/356911/). The most relevant part is this: "It seems I was overenthusiastic when sending that email to the couchdb dev list, and left out an important word: 'can' be replicated :)"
In other words, this is an optional service that you can choose to use -- no default install is going to send your info to Canonical.