Not sure if you watched the keynote or not, but iCloud is not really giving up ownership of your data - all it does is keep ALL of your data synced between ALL of your devices once developers get iCloud elements added to their apps. For example - let's say Microsoft releases an Office app for iOS. They add the iCloud elements to that app, and updated Office for Mac to include them as well. Then, the ball is rolling. You edit an Excel spreadsheet on your desktop, and in seconds it is automatically pushed out to your iPhone and/or iPad. You grab your mobile device and head to the field to collect data. When you get home at night, all those changes have automatically been pushed back to the desktop - with NO interaction by you. All of it takes place in the background, and completely automatically. Your data is still stored on your computer and mobile devices, allowing you to retain ownership of it. The Chinese could nuke the big, new Apple data center in NC and you wouldn't lose a thing. All of your apps still run locally.

The key to this is it requires nothing from the user. Many current cloud services require you to add files to them and retrieve them later on other devices - extra steps and a learning curve for newer users. With iCloud, you log in once on each device and you are set. This will work on email, calendars, contacts, data, music, pics, everything. As I stated earlier, some elements of this are not new - Google has parts of this, Amazon has parts of it, etc - but this is the first time there will be a comprehensive system all in place under one roof.