But if he can prevent transactions and take all the freshly generated coins to himself - isn't it technically taking over the network?
Anyone who has such hashing power has to choose between assaulting the network and participating honestly within it. If said person has 51% of the hashing power, and participates honestly, he can capture 51% of the newly generated coins. He could choose to reject every transaction, and simply publish empty blocks, but this isn't an attack on the network, really. It does no harm, since transactions can still be expected to be processed by the miners who capture the other 49% of blocks. However, such a person could choose to prevent all transactions, but to do this he has to turn his miners to the task of
reversing all of the blocks that are created by other miners, so he would still only be able to capture about the same number of blocks over the same time period. The effective hash rate of the network would be cut in half, but only if the attacker is successful at reversing all honest blocks before another honest block could be built upon it. The odds of this continuing for any extended period of time is remote with only 51%.
I know it is unlikely.
But you say that he can deny to publish all the transactions.
What I think would be more dangerous is if he defines a filter that accepts some transactions, but not others.
It could turn into corporations ruling over what can and what cannot be sent through.
So it's more likely to happen
