Use something like todo-backup to backup your files if you setup syncs using Spider-oak.
Spider-oak syncing is slow as molasses. I signed up for 100 gigs and synced up 'my documents' across 3 computers. I installed a new hard drive on my laptop and restored the sync. Of course it took days to sync up, in fact it's still working on it, I'm used to that slowness already. But over 2 days Spideroak systematically deleted 62036 files and 7150 folders, because the laptop didn't have all the files and folders, it decided that I must have deleted everything.
I went into the recycle bin in Spideroak to look for my files and folders, they were there, but there is no way to sort by date deleted column. At the very least, you should have a way to sort by date deleted to make recovering from these disasters not take a full week of plodding through each and ever folder and subfolder.
Luckily I used another product to backup and it was easy to restore the files. Using spideroak recycle bin would have been a mind-numbingly slow and cumbersome process. The warning about 'exact file structure' when restoring a sync needs to be clarified, why can't it just say 'if you have some folders and files missing on this new pc we are going to delete them from all your other pc's"