I am a photographer and upload a lot of photos online. Both to Facebook and flickr. But these sites although great for sharing photos with the world are not ideal backup solutions.
I love Ubuntu One and try to utilize it as much as possible but frankly I am more than a little lazy. So I more often than not don't back up to U1.
The same can also be said about my document uploads to Zoho and class projects.
Copy on Upload
The idea here is whenever a user uploads a file Ubuntu should automatically copy it to the Ubuntu One folder. This would likely be implemented through a browser extension.
Although the idea and basic implementation are simple there are issues that must be considered. These include size, bandwidth and privacy issues. As such the user may not want to copy every single thing they upload to Ubuntu One. But having a popup come up every time something is uploaded is intrusive and annoying.
These issues could be combated through:
-A strong settings framework
-In browser dialogues (see the new "save your password/settings?" dialogues in Chrome/Firefox)