The new Ubuntu One feature is nice but some official Ubuntu flavors may need to opt out.
Here's a few reasons:
1. Ubuntu GNOME includes the U1 libraries but not the file sync app and because of Qt it's a significant amount of space to install ubuntuone-control-panel-qt (apt says 29 MB packages, 109 MB installed). While the feature is more than just file sync, it feels weird promoting a service that is missing a major component by default.
I also don't like the U1 app's design especially on GNOME and filed a few basic UI bugs when the redesign happened, bug 939839, bug 939853, and bug 939869 with zero response.
2. It's not working here on Ubuntu GNOME. I'm not sure if that's because USC and so on haven't been updated for it or whether it needs more UOA plumbing. GOA simply works better than UOA for Ubuntu GNOME's needs at this time but I don't see any one stepping up to write a GOA provider now.
3. It sounds like Edubuntu may want to opt out. https://plus.google.com/118060934321492774758/posts/9KWT21ehG6i
ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: ubiquity 2.15.14
ProcVersionSignature: Ubuntu 3.11.0-4.9-generic 3.11.0-rc7
Uname: Linux 3.11.0-4-generic x86_64
ApportVersion: 2.12.1-0ubuntu2
Architecture: amd64
Date: Wed Aug 28 23:46:49 2013
InstallCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.11.0-4-generic root=UUID=da074346-bf87-4cf5-a9ec-8589cb501c4e ro quiet splash vt.handoff=7
MarkForUpload: True
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)
With latest ubiquity upload, the page is only shown if:
* --no-sso command line argument was not specified
* UBIQUITY_NO_SSO environment variable is not present
* ubuntuone-client is installed (on the cd image)
In terms of technology used, the page does REST queries to login.ubuntu.com and gets an authentication token which is stored encrypted in the gnome-keyring. Thus any applications that do authenticate to ubuntu1 services with gnome-keyring api can, with user's permission, access u1 services. There is no dependency on neither qt, gnome nor ubuntu online accounts frameworks.
if you still want to opt out, imho it's best to e.g. add .disk/environment file which would then be sourced by ubiquity to allow setting many of the environmental overrides that ubiquity supports on per flavour basis and cd-image build time.