Above and beyond that, the effect of high block times is that centralized miners gain a significant advantage over decentralized ones. The current block latency

Above and beyond that, the effect of high block times is that centralized miners gain a significant advantage over decentralized ones. The current block latency of the Bitcoin network is in the order of a number of seconds. As we know that current mining pools are indicative of the best connected (many of them have private peering and significant numbers of edge router nodes), we can assume that the majority of the network will be even poorer than this. In some testing the difference between a Stratum socket on the top 4 pools announcing a block was often up to 3 seconds. For a 12 second block time in Bitcoin, the network would likely collapse down to just the biggest pool, as everybody else would have a disproportionately high number of orphan blocks. Sensible miners would need to move to the biggest pool in order to avoid a significant double-digit percentage losses. > I thought the risk of a split chain was tied mostly to the wall clock, not the block count? This is a correct statement to make. The number of blocks considered to be safe is completely irrelevant, and only has the effect of denoting the time on the wall. An hour for 6 confirmations in Bitcoin wasn't chosen so much because it was 6 blocks long, but because it is a reasonable tradeoff between convenience and security. If the block time had been 5 minutes you would need 12 to get the same level of confidence in a transaction. I don't understand why the Ethereum developers appear to think otherwise.