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From what I can tell, the Ethereum blockchain just stores accounts and balances - why did the original Bitcoin developers choose the method of storing all transactions for validation instead of just account balances? It seems like that would reduce blockchain size on disk quite a bit...

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possible duplicate of Can Bitcoin-Qt be configured to trim the blockchain? – Nate Eldredge Jul 30 '14 at 16:31
@NateEldredge I'm not asking about blockchain trimming, I'm asking about the original decision to implement this type of database altogether – pinhead Jul 30 '14 at 17:16
up vote 6 down vote accepted

In order to be sure that an address balance is correct, you need to check that all the transactions on that address are valid. So in order to generate a ledger that you trust, you must first download and verify the entire block chain.

Once you've done this, in principle, you could delete the block chain itself and just keep the ledger. However, remember that Bitcoin is a peer-to-peer system. So you keep the block chain so that new users can download it from you.

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Ah that's what I was overlooking: clients that haven't been running since the genesis block need proof that each account balance is accurate – pinhead Jul 30 '14 at 17:25

Exactly the same question was asked to a Bitcoin developer (Peter Todd) during the Bitcoin 2013 Conference.

You can watch his answer here

For those who are too lazy to watch the video the short answer is that they are doing it for security reasons.

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Video can't be skimmed for important bits like text can. So not wanting to watch video isn't laziness; it's disliking the delivery medium. – Almo Jul 30 '14 at 22:38
a bit of humor never hurts ;) – 109fa68a145b Jul 30 '14 at 22:54
Humor?!? What's that! :) – Almo Jul 30 '14 at 23:12

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