Here is one way to store your stuff more securely in the Ubuntu One cloud.

0) If you mess up and need to start over again follow these directions to completely remove Ubuntu One and start again.

1) Install the file encryption program Cryptkeepter with sudo apt-get install cryptkeeper at the shell, or your favourite package manager. This uses an encrypted file system called EncFS for pass-through file encryption - essential for having your stuff be readable to you but gibberish to anyone else.

2) Setup your Ubuntu One account by going to https://one.ubuntu.com and following the directions.

3) Start up Cryptkeeper (Applications --> System Tools) which will place a new icon in your tool tray.

4) Create a new sub-folder in your Ubuntu One folder (eg. "U1-safe").

5) Click on the Cryptkeepter tool icon and select "New Encrypted Folder". Choose the folder that you created in step 4. It will prompt you twice for a passphrase - make it a good one. You should see your Ubuntu One tool icon announce "Updating Ubuntu One" right after this and a new disk volume should appear on your desktop and in your file browser that is named the same as the folder you created in step 4.

6) Copy or move the files that you want to be securely stored in the Ubuntu One cloud into the new mounted drive on your desktop. You should be able to see them normally as long as this folder is mounted through Cryptkeeper.

7) On your other machine(s) follow steps 0-4 but on step 5 choose "Import EncFS Folder" instead of creating a new one. You will be prompted for the passphrase before it will give you access to your files.

8) The syncronization delay on Ubuntu One seems to vary but this should store any files in your encrypted folder as cipher text on Ubuntu One. You can confirm this by examining your folder through the Ubuntu One web interface. Be sure that all you can see is gibberish and  do this before putting anything sensitive into your folder for cloud storage.

Good luck and keep safe!