Thanks nussbi, great answer. Just on point 2, as the number of transactions grow, my understanding is that all the nodes have to have a copy of the transactions

Thanks nussbi, great answer. Just on point 2, as the number of transactions grow, my understanding is that all the nodes have to have a copy of the transactions (otherwise how could I verify the coins source coins without a complete trail). Have they come up with a clever way around this or am I missing something?