They can't set balances to whatever they want. They have to justify each switch from ledger to ledger with signed transactions. (Just like miners in Bitcoin can

They can't set balances to whatever they want. They have to justify each switch from ledger to ledger with signed transactions. (Just like miners in Bitcoin can choose the transactions to include in their blocks but can't just create Bitcoins out of thin air or teleport them from one account to another.)