[vidarh]

Storage is the easy part. The problem starts when you want to allow the server to do at least some limited operations on the data without having to decrypt it.

They mention search. I wrote a comment elsewhere in this thread about some simple approaches to doing that while reducing information leaks (that'd potentially make more serious attacks on your documents viable if you're not very careful), but if they have some cryptographically sound mechanisms to outright prevent information leaks but still allow searches for example, that'd be a big deal.

In theory, homomorphic encryption might eventually let us let the server run almost any algorithm over the encrypted data without decrypting it, but for now, they are way too slow to be practical for most things.