Nothing will stop people bringing on a huge number of nodes at any cost. Making this hard is the issue. So hard as in bitcoin means expensive (more expensive to attack than what you would get) and the network effect means this number gets hard very quick. I do not think there is any such network (including bitcoin) that can prevent a massive attack from destroying it. Its all in the difficulty. If this has been your debate then I agree, no matter what sheer weight of numbers will eventually win.
This is where we use cryptography and a very efficient DHT implementation (this part has never existed), to:
1: Identify nodes (PKI)
2: Measure the distance from a crypto secured node to another in xor space
3: Use distance from an action (or node, or data element etc.) to evaluate responsibility and authority.
4: Use the non euclidean distance to create a huge network of connected events and groups in xor space (like a 3d connected venn diagram)
5: Where owned malleable data (such as directory entries, coins, contracts, computations etc.) are involved then use signatures as authority to mutate, but only allow the responsible nodes to give this data
6: Use network synchronisation, (this includes accumulate and account transfer as per vault paper in wiki) to ensure the network atomically can mutate any data.
7: Maintain strict deterministic consensus groups to manage a chain of events that complete a ‘transaction’
Hope that helps a little, it does need detail and a doc, there will be a vault paper soon from Greig at the Uni, another paper specifically on consensus chans is also required. It need to identify all the above plus access, account creation and immutable data (self encryption). The problem is the reading required is huge, This is why I like a whiteboard, I have used this with many many professors and industry leaders to go over the whole process. It is huge and very hard to summarise as you may imagine. It’s hard to summarise this, as is bitcoin (i.e. how does the p2p network work in bitcoin (hint it’s not detailed in the paper) as this is an essential part of bitcoin working).