[epscylonb]

You can't put arbitrary data in a transaction, at least not very easily. The bitcoin devs are pretty clear that the bitcoin network and blockchain should not be used for messaging or store non transaction related data.

What actually is happening here, is that miners have the opportunity to put a small amount of arbitrary data in a block when they mine. Ideally this is should be random data, its purpose is to change the data being hashed so you get a different hash each time you try.

In my view the author of bitcoin set a bad precedent by including a newspaper headline referring to bank bailouts in the very first block. However I can't begrudge him for that too much. Since 2009, people have included prayers and accusations of illegal activity (trolling) in blocks.

Assuming increased bitcoin adoption, I see mining getting more and more centralized, already I don't think any of the major mining pools would be silly enough to include CP or other illegal content. It would take many blocks to store a non trivial sized image in the blockchain, and if they put a link in instead then of course the host could be taken down.

[rlpb]

> You can't put arbitrary data in a transaction, at least not very easily.

No; it's very easy. Anyone sending Bitcoin can add arbitrary data in his transaction; no need to be a miner: https://en.bitcoin.it/wiki/Script#Transaction_with_a_message

[eric_bullington]

Satoshi included a headline in the blockchain to serve as a timestamp to prove that mining had only started at the time of his public announcement about the project. However, the particular headline chosen as a timestamp was probably not selected at random.