SpiderOak's plans are pretty cheap. Also you could use S3+Glacier for storing just about anything. I would be surprised if AWS scanned your files for "inappropriate" content.
>Offensive Content. Content that is defamatory, obscene, abusive, invasive of privacy, or otherwise objectionable, including content that constitutes child pornography, relates to bestiality, or depicts non-consensual sex acts.
So, most pornography should be okay.
Most pornography could probably fall into a reasonable reading of “obscene, ..., or otherwise objectionable”.
Why would you be surprised? I'd go under the assumption that anything you give to them could trivially be scanned.
I used SpiderOak for a while and though it started off with promise, it just isn't up to scratch compared to other services.
Plus its mobile application is horrendous.