Is an atto-ether, or one quintillionth of an ether really necessary? That's 0.000000000000000001 ether. A billionth of a billionth of a unit. In other words, there are 2-3 orders of magnitude more units in a single ether than there will ever be satoshis in the entire Bitcoin system. (2 quadrillion 100 trillion satoshis). A single ether is around 476 Bitcoin systems in terms of units. So if you invest 10 BTC in Ethereum, you will have as many units as 9.5 million Bitcoin systems. If 90000000 ether are created to start the system, that's 42.8 billion Bitcoin systems in terms of units. Isn't that a little ridiculous? Doesn't this kind of divisibility make the numbers on the other side of the decimal irrelevant? It's inconceivable.