SpiderOak encrypts your files before upload, and they don't have the keys. ( https://spideroak.com/whyspideroak https://spideroak.com/whyspideroak ) Thats why

SpiderOak encrypts your files before upload, and they don't have the keys. ( https://spideroak.com/whyspideroak https://spideroak.com/whyspideroak ) Thats why at the end of the post they say that even if they decided to deduplicate in the future, they would have no way of retroactively doing it.