I don't understand why people think shorter block times are better. It only means you need more blocks for the same security, thus meaning the block chain just gets needlessly bigger. Many Bitcoiners understand that, but many Altcoiners don't want to understand that, because that would mean their Altcoin has no advantage at all.
The real problem with short block target times is network propagation. Once a block is found, it's not relayed to the whole network instantly. If you see a cryptocurrency with short block target times, but still not a considerable amount of orphaned blocks, you know that the network of that coin is not properly decentralized, but rather centralized.
Yep, and you have to do a bunch of back-bending tricks to accommodate the fact that when you scale up the network, disparate parts of that network will have different states.
The ethereum blog post attempts to fine-tune this, but then you are left with a larger problem, the attack against the network becomes the alt-coin's biggest flaw. If I'm running an ISP, or I'm a government dedicated to screwing up your fast-confirmation coin, all I need to do is introduce random delays that screw your entire finely-tuned setup to dust.
But hey, that wouldn't happen, would it?
