You're right in your point about backups. These cloud services present quite a problem in the sense that they're structured to accommodate massive amounts of data. Often times this data is generated within the service itself with no means provided to extract it. So even if the user wanted to be responsible for backing up their data it's often times impossible. Moreover, even if the user wanted to AND had the means to do it, it could be a massive amount of data to sync up -- more than your average user is going to take the time to do.