"UbuntuOne will eventually be integrated into Ubuntu. Users will
be able to share files with others on the service. It will be half
backup and half social. No matter whether there's an open version
of the server or not, the vast majority of users will be on
UbuntuOne instead of WannabeOne because that's where everyone else
is and getting set up is much more convenient to use the included
client than downloading a different client setting it up with the
other service.
"In both cases, Canonical gains little by playing both sides of
the fence, offering closed-source solutions as an open-source
business, but it loses a lot of community support."