The thing is, Dropbox treats their version as the primary copy. For instance, I added several directories to Dropbox, and decided that I didn't want it syncing a few of them. I de-selected the directories under "Selective Sync" and it removed them from my computer - even though my computer was the original source.

Yes, sync != backup [1].

I do agree with you but, I can tell you that selling backup service is harder than you think. Also as pointed by paper [2], the human error accounts for ~50% of all system failures. And the worst thing is that majority of users who accidentally delete data, don't even notice data loss until lost data is needed and they don't recollect doing something wrong.

What I found out interesting that people (i.e., small business owners) will are scared of losing a credit card (even though you can call the bank and cancel your lost credit card and get a new one - inconvenience but not a big deal), but they will not backup critical company documents and data (even if they lose them the company will be pretty much closed - there is no "bank" to go to and get data back).

[1] http://blog.cloudhq.net/post/33844549768/the-difference-in-d... [2] http://roc.cs.berkeley.edu/talks/pdf/HP.pdf

Not sure it is harder than I think. Other than that, I haven't nothing else to disagree with. :)