Here's an interesting scenario: the Opera installer asks you if you want to install the "Freedom" service, if you agree, it installs a background server (always on, launched on start up). This service is a local web server + web application that provides a user interface to all your local data : your address book, your music (you can listen to your mp3s with a flash player, streamed), your calendars, your documents, etc. Of course the access is protected by default.

The networking issues aren't that problematic : the local app would periodically update a central database with the computer's IP (dyndns.org has been doing this for years) and an available open port. So when you identify yourself on the http://freedom.opera.com service, you are redirected to http://YOUR-COMPUTER.freedom.opera.com:OPEN-PORT/.

So basically, Opera would be going against the current trend of putting all your data in "the cloud". Sounds interesting to me…