As a terrorism expert, I was immediately confronted by the fact that under certain calculations, the bombings in Madrid last week were 911 days after September 11, 2001. provides on of the best explanations on the coincidence that I have seen to date, including the following explanation for why we care:

So why do some of us continue to find significance in these types of coincidences? One answer is that it gives us back a sense of control over a world gone mad. Other than cower in our homes, we can do little to protect ourselves against an enemy who might strike against anyone, anywhere, at any time. Being able to find patterns, even obscure ones, between terorrist-related activities allows us to think that we can take back some measure of control; that we can indeed discern when and where the next attack might come if only we stay alert for hidden messages and use the proper keys to decode them.