[intelliot]

Technically speaking, no.

patio11: that is not how the Bitcoin protocol works.

Even if 99% of the Bitcoin miners agree, they cannot create extra bitcoin; it is simply impossible because that is not something that miners control. Every full node (client) on the Bitcoin network verifies the validity of each block. A block that created more bitcoins than allowed by the protocol would be rejected by the clients (and the miners who follow the original rules). The "extra" bitcoins would be on a hard fork and thus invalid to anyone on the main (original) blockchain.

More info: https://en.bitcoin.it/wiki/Weaknesses#Attacker_has_a_lot_of_...

[patio11]

You're right, the defecting miners would have to convince people to download a new client, or convince the sites which those people access Bitcoin through to use the new client. Sorry, should have mentioned that, but I thought the thrust of the concern was "Could we just rewrite the rules of Bitcoin to make this retroactively not happen?" And the answer to that is "Yes, but the community would explode."

[judk]

What you are describing has already happened once, with the rollback and the 0.7 -> 0.8 version upgrade.

[ProblemFactory]

But the protocol can be changed.

If the most common bitcoin clients are updated to allow this "bonus", and at least 51% of the network installs this update, their blockchain will become the authoritative one. Older or other clients will have to accept it if they still want to participate in the chain.

[VMG]

The authoritative blockchain only determines the order of valid transactions, not which transactions are valid.

A transaction that conjures Bitcoin out of nothing is certainly invalid. Patio11 got this wrong.

[ProblemFactory]

The validity of transactions is checked by the individual bitcoin clients. After all, something, somewhere must check if they are valid according to the protocol rules! And this client code can be changed to anything at all, as long as most miners agree to update to it.

Transactions that make up bitcoin out of nothing are already used as rewards for mining a block.

[VMG]

Individual clients don't have to use the same client that miners use.

If 51% of miners start using an inflationary version of Bitcoin "Bitcoin-QE", but the clients (exchanges, merchants, wallet providers, etc) don't approve, they won't update the client and use the partition of the network that is secured by the remaining 49% of miners. People wouldn't want to accept the Bitcoin-QE mined on the inflationary branch and the investment wouldn't pay off.

Of course Bitcoin-QE miners could start an attack on Bitcoin in other ways, but that also woudn't be necessarily economical.

It's very hard to tell what 51% will do, but it is clear that you don't have full control of the currency.