Dropbox is private. And  while the 2GB free option doesn't give you a whole lot of online space, so it's no good for music, pictures or videos, it is ample for my word processing documents, spreadsheets, databases, etc, plus all my browser bookmarks, address book, notepad, and small web pictures from Facebook etc. And I've still got half of the 2GB left. "Time Machine" is an automatic backup system for Macs - plug in a 500 GB external USB hard drive, nominate it as your computer's backup disk, and then just forget all about it. It keeps hourly backups for a day, daily backups for a month, and weekly? monthly? backups for as long as you have room on the disk.  Like Dave, I'm a 'belt and braces' man - I also have a bag of memory sticks ranging from 2GB (personal documents) up to 64GB (my iTunes library)