Matematically sybil attacks cannot be prevented, what you can do is make it expensive to do sybil attacks, which will make it increasingly more expensive as more servicenodes come online. and lets for the sake of arguement say i want to do a sybil attack.

first thing i need is spr, so i start buying up spr, as i buy more and more, less is being sold, which means the price of spr goes up, exponentially, so basically as i get closer and closer to own a big enough amount of servicenodes, i will end up having to pay increasingly more and more for adding more nodes.

second part is logisitics, the more service nodes i want running for this, the more server infrastructure i will need to buy, which is a hidden cost not too obvious in the beginning.

now im ready to try and do a sybil attack, problem is, i can never own enough service nodes to garantie a success before the network will start to look on my servicenodes as suspicious, and i can end up with all my nodes being kicked off for misbehaving..

since the servicenode network needs a system to protect itself, it will use the power of voting, where each node has 1 vote, majority will always win, and end up overruling the nodes i have set up to try attacking the network.

so, i need 50.1 % of all servicenodes to do this to win the voting element, how expensive is this going to be, will determinate if it would be feastable to try attacking the servicenode network, and get it to do my bidding..

that, is the power of collateral.