According to the US, if a company is registered in the US, all data they hold anywhere in the world is fair game. So this includes all servers used by Microsoft, Amazon and Google anywhere in the world according to the US. And in the last few days there has been another example of this:
"Google is the next major company to admit Patriot Act issues, as it admits to handing over data held in a European datacenter back to U.S. intelligence." ZDNET, August 11, 2011
I am not a lawyer and not related to Ubuntu One/Canonical and not a lot of users here are legal experts with knowledge about this situation so an answer to your question will all be conjecture. And it also depends on how stubborn the EU is about enforcing own law and opposing the US Patriot Act.
Ubuntu One Terms of Services
This agreement is governed by the laws of England and any dispute will be heard by the courts in England. Failure by Canonical to enforce any right or provision of this agreement shall not constitute a waiver of such right or provision. If any part of this agreement is held invalid or unenforceable, that part will be construed to reflect the partie's original intent, and the remaining portions will remain in full force and effect. The terms of this agreement do not affect your statutory rights.
Ubuntu One is based in the UK so the company is subject to the EU laws and the
European Data Protection Directive. So the answer to your question should be
no Ubuntu one is not affected by this if you store the data on a EU server
Any data stored on a cloud worth protecting should be encrypted. Might not stop the US from getting it and also might not stop the US from decrypting it but it should be made as problematic as possible ;-)
I haven't used the Ubuntu One service, but it looks like a viable alternative to DropBox. I've used Dropbox for several months now, and I haven't had any issues with it. The only nice thing about Ubuntu One is that is has 5GB free storage. Dropbox you only get 2GB free.
They also offer a Windows7/Vista program for Ubuntu One. It looks very similar to Dropbox. https://one.ubuntu.com/downloads/
Yes it is possible. The best way to archive this with a per file encryption is with encfs:
The general principle is that you have a (optionally hidden) encrypted folder inside UbuntuOne/Dropbox where your files are stored, but you access them though another folder, where the decrypted files are shown. Any File you add to the decrypted folder will be encrypted and put into the encrypted folder:
Decrypted folder ←encfs→ Encrypted Folder (inside UbuntuOne/Dropbox)
On another computer the encrypted folder is synced by UbuntuOne/Dropbox and can also be decrypted on the fly.
Install encfs version 1.7 or greater
Setting up the Drive on the first computer:
You should now have your encrypted drive mounted (it will be displayed like a mounted usb-drive)
Importing the drive on other computers:
Cross Platform compatibility: