If the average consumer thinks the problem bitcasa is solving is a strong enough pain point and use bitcasa's product anyway, then I can see SpiderOak moving into this area regardless of the security issues it brings up. Unfortunately, the average consumer doesn't care enough about security for "implementation details" to sway them if they have a pain point that the product solves - even if those implementation details make a world of difference in terms of privacy. There are already products out there that store files from a user's devices (laptops, desktops, etc.) on the cloud with no mention of not having access to the encryption keys if they do do encryption: https://www.sugarsync.com/ is an example.

A little off topic: I do think that the community has done a good job drilling it into the average user to look for the green bar and padlock in their browser when they go to their bank's website. It means Security. heh.