Subject says it:
Ubuntu One is going away, most of it anyway. The most important part for me and
probably a few or more of you is that the Dropbox-like synchronized storage is
being shutdown with all content to be deleted in July.
Here's a link to read the basics.
Canonical to close Ubuntu One
The silver lining in this dark cloud (pun intended) is the fact that
Canonical will be releasing the source code for the serverside
components of Ubuntu One storage. So it will be possible to run Ubuntu
One on your own server, and you may start seeing providers doing exactly
that in the future.
