Storj guy here. All of the actor vectors you described are addressed in the our whitepaper or a blog post.
I read the white paper last week.
1) Sybil - Bonds and unique pieces
There is no way to do proof-of-storage that is robust. The only way is to make some assumptions about latency of propagation to a centralized copy of all files, but that can be gamed. Propagation is not proof.
2) Illegal content - Greylists
The
Storj FAQ confirms these are opt-in, and not forced. Thus I maintain my point that the Storj protocol can become banned (refused) by Hosts (and even ISPs). We are moving into totalitarianism and increased government control over the internet.
This direction of enabling theft of copyrights is begging for your project to be attacked and fail.
3) Bandwidth vs storage - pay for both
Pay how? Micropayments for each access to bandwidth?
How to pay for storage when it is decentralized with unbounded replications and can be Sybil attacked.
Sorry these decentralized systems are doomed. The
concept can't work.