Good ideas can often be subtle. Boiled down to utter simplicity the difference between facebook and myspace may seem to be tiny. But that's not the case. Another term for subtlety may be "precision". The difference between facebook and some other seemingly similar site may seem subtle but by the same token it may actually be a difference in precision, with facebook hitting a tiny target (a correct mix of complexly interacting features and design) that others missed.

You see this sort of importance of precision/subtlety everywhere. The difference between the best selling automobile and the 20th best selling automobile in the same class is often a long list of subtle, yet important differences. Also, what may seem like subtle, some might say inconsequential, differences on casual inspection may in fact be jarring, fundamentally important distinctions. The addition of 1 tablespoon of salt to a bowl of soup instead of merely a pinch changes the flavor dramatically, even though in either case the salt is only just a tiny, tiny fraction of the ingredients.