That said, people DO use DropBox as backup.

If you take a walk around the British Library and asked every PhD student working there how they "Backup" their research and work in progress, I bet every single person who believes that they have a backup will say "Dropbox", and the only exceptions will be a few who don't really have a backup.

I know that because I ensured my girlfriend does have a real backup solution in place that is tested. Not one of her peers seems to.

DropBox is used for backup because they've made file sync so damn easy that most people can be convinced that if a file exists in many places, it is backed-up.

My whole point is that now storage for long term backup is priced in a way that is affordable to most, that consumer services may emerge that offer true backup to consumers and can successfully migrate people from lesser solutions (DropBox, stacks of CD-ROMs, etc).

One of the things about backup is that it needs to be easy. Currently the size and cost of backups make it expensive, and the only way to reduce the cost makes it difficult (HDD local copies stored at a friends' house for example).

By reducing the cost, perhaps we can finally increase the ease... and then a day may come in which most people have a real backup solution.