Canonical's John Rowland Lenton said here: "Our situation is rather unique, and we were unable to resolve some of the issues we came across. We were thus unable to make CouchDB scale up to the millions of users and databases we have in our data centres, and furthermore we were unable to make it scale down to be a reasonable load on small client machines."
Lenton informed in his post because of this "we are turning off most of our CouchDB-related efforts. The contacts, notes and playlists databases will continue to exist on our servers to support the related services, but direct external access to the underlying databases will be shut off. Any other databases will be deleted from our servers entirely".
Ubuntu has also informed that the desktopcouch that has been developed since last 3 years, which is a desktop service (and related library) to access CouchDB more conveniently. it will no longer be developing desktopcouch; in fact, and has offered if anybody wants to take over. For the upcoming 12.04 the Ubuntu One packages will not depend on desktopcouch nor couchdb in any way, and its recommended the distribution seriously consider whether they want to continue having the package in main, especially if no maintainer shows up.
Based on the issues that surfaced and whats learned Ubuntu would like to go ahead and allow a natural deprication of CouchDB fucntionality and instead design its very own, merely a layer of abstraction and the definition of an API that will allow them and others to build what is needed ontop of existing tools.
Lenton said "We're calling it U1DB for now, until it comes of age. If you're interested and techincally inclined you can follow our progress on lp:u1db; unfortunately our timing and resources are such that we can only promise the reference python implementation will be ready in time for 12.04, and thus 12.04 will ship without Ubuntu One having a solid story around synchronizing arbitrary structured data".