I'm a bit confused about this.

I've found a post from Gavin in reply to ribuck saying:
"Quote from: ribuck on January 25, 2011, 03:17:27 pm
The analogy doesn't stretch further than being a cute graphic. Individual bitcoins don't exist in any meaningful way, nor do the individual specks of bit-dust. There is no notion of 21 million coins, numbered 1 to 21,000,000.

"Sure there is-- block 0 contains coins 0-49, block 1 coins 50-99, etc.

If you get sent 500 bitcoins, they can all be traced back to generation transactions, so you "own" a bunch of little pieces of land in bitcoin-world."

The (otherwise excellent article in the economist) says:
'Bitcoins do not resemble banknotes with unique serial numbers.'


Of course, I'm inclined to take what Gavin says over anyone else, but I want to make sure I'm not misunderstanding this.

I had in my mind the idea that each bitcoin could be traced back through all its transactions to its generation (no matter wether it was mixed with other bitcoins or not).


I'm a money freak wanting to write another blog post about bitcoin. Already posted a question about the inclusion of transactions in the block chain to which I received a very helpful answer. Your thoughts are appreciated.
-Jon

Hello. First I got to congatulate everyone involved in the bitcoin project - you're an inspiration. I'm keen to write something for my blog that explains some of the technical aspects of bitcoin in a non-technical way, hopefully exploring the nature of money along the way. I've spent a while reading up and trying to understand things. The bit I seem to get stuck on time and time again is the relationship between transactions and blocks.

Any clarification you can give would be very much appreciated. Here's my problem:


I read in the wikipedia article that generating nodes have no obligation to include transactions when they create a block.

However in the bitcoin wiki/blocks section it says 'Bitcoin transactions are broadcast to the network by the sender, and all peers generating coins collect them and add them to the block they're working on'

I also read that the totality of transactions are hashed (with individual transactions NOT being hashed). (I assume this means ALL transaction since genesis, rather than in an individual block?).

So when you say nodes have no obligation to include transactions, does it mean that they can just use the last transaction hash and work from there?


Thanks
Jon