What do you do when cloud storage fails you? First, some background.

A popular cloud storage provider (rhymes with Booger Link) damaged a bunch of my data. Getting it back was an uphill battle with all the usual accusations that it was my fault, etc. Finally I got the data back. Yes, I can back this up with evidence. Idiotically, I stayed with them, so I totally get that the rest of this is on me. The problem had been with a shared folder that works with all 12 computers my business and family use with the service. We'll call that folder the Tragic Briefcase. It is a sort of global folder that's publicly visible to all computers on the service. It's our main repository.

Today I decided to deal with some residual effects of the Crash of '11. Part of the damage they did was that in just one of my computers (my primary, of course) all the documents in the Tragic Briefcase were duplicated in the Windows My Documents folder. I finally started deleting them. But guess what.

Though they appeared to be duplicated in the file system, removing them from My Documents on the primary PC caused them to disappear from the Tragic Briefcase too. They efficiently disappeared from all the other computers' Tragic Briefcases as well. So now, 21 gigs of files are gone, and of course I don't know which ones.

I want to avoid this in the future. Apart from using a different storage provider, the bigger picture is this: how do I back up my cloud data? A complete backup every week or so from web to local storage would cause me to exceed my ISP's bandwidth. Do I need to back up each of my 12 PCs locally? I do use Backupify for my primary Google Docs, but I have been storing taxes, confidential documents, Photoshop source, video source files, and so on using the web service. So it's a lot of data, but I need to keep it safe. Backup locally would also mean 2 backup drives or some kind of RAID per PC, right, because you can't trust a single point of failure?

Assuming I move to DropBox or something of its ilk, what is the best way to make sure that if the next cloud storage provider messes up I can restore?