Are you sure? I think it's definitely a significant enough amount to be mentioned with the others either way.
Not to mention the fact that a users interaction with Facebook is completely different from their interaction with Apple. Most people keep especially private data off of Facebook, but practically no I-phone user stops to think if a photo might be incriminating/embarrassing in the future before they take it. And that's just Photostream.
People backing up their devices to iCloud stand to lose even more.
Enough to be mentioned. To be used as the primary example and including Google as others?! Sounds more like an author that is getting paid for every Apple mention in an article title.
- Mail and calendar for people who use the iCloud services.
- Reminders.
- All documents (e.g. Pages, notes) synced to iCloud.