If someone some how manages to encircle your node with a million of their own (i.e. your node is only connected to theirs) then what are they going to do? If th

If someone some how manages to encircle your node with a million of their own (i.e. your node is only connected to theirs) then what are they going to do? If they try to filter blocks or tamper with blocks then your node will detect that and disconnect from them. Ultimately, your node is hard coded with a list of IP addresses, so that if all else fails when trying to obtain good connections with other node (DNS etc) then it can connect to those. Regarding the impact of a single node on the network, that node is a way that _you_ can vote on what bitcoin is. You could equally shut it down and vote by connecting through someone else's node, but then you'd be trusting that their node defines bitcoin the way you want to. In other words, the people decide what bitcoin is, not individual nodes, but the nodes that people connect through define what they are voting for. If you want to be _sure_ that your vote isn't being misdirected, that what the node is reporting as bitcoin really is bitcoin then connect to the network through your own node.