Proof-of-capacity whitepaper

Perhaps this should be moved to NebulousLabs/Experimental? Or maybe we should just have a Papers repository...
risky statement, 'byzantine' means that they'll do whatever they want for whatever reason.

Instead, we make sure that other types of attacks are cheaper, or we make sure that an expensive attack on the network doesn't affect the network negatively.

In this case, since we don't define a whole network, we can't make any assumptions that are that strong. We just have to acknowledge where the weaknesses are and explain their magnitude.