If failures occur at random and the vast majority of nodes are those with low connectivity, the likelihood that a highly connected node would be affected is negligible. (coindesk.com)
After activation, if a rogue miners tried try to spend «anyone - can - spend» outputs he would effectively be performing an attack on the economic majority of nodes who enforce the new rules and so those miners would have their blocks orphaned by the network. (segwit.org)
If an updated ledger is broadcasted that a majority of the nodes on the network are not in consensus with, then a node will not update to retain that copy of the ledger because it is not a truthful and honest representation of the transaction data. (coinsnews.com)