Dropbox is a little bit different than other tools. It is not primary designed for backup, but for automated file sharing between two computers and access to them through the web interface.
After registration and installation this controlling software appears like regular folder, but all you place into it will be automatically synchronized with online server. You can add “Share” attribute to them, and make it shared publicly or only for selected users of Dropbox. Using Dropbox is extremely easy and users they are able to work with regular folders and files can use Dropbox the same way .
Maybe there is just one small handicap – Sharing. If you like to share big folder (in gigabytes) the person who you share with has to obtain at least the same size prepaid space.