Copypasting my old post here:
It's hard to prove. If you have file "1.jpg" stored in /home/user/pictures which contains illegal picture - it is "storing of content". But if you have blockchain with encrypted picture which could be picked from it only with help of special software... Uh, I can write a program that will get 128 kilobytes of symbols from Windows system common files, and - bah! - it is illegal content! So ALL users of this Windows version can be blamed.
Edited: and yes, if you are afraid, you can store blockchain in encrypted virtual machine or VPS.