How much money would be lost by not opening business though? We already have one major American city not functioning... we can't let another go offline for a threat. As someone else said, if they close down tomorrow, why would the would be evil guys not just wait till Monday?
Right - and also it is important for them to see that the only reaction from us is us getting tougher, not weaker and in 'fear' of them.
Maybe by Monday we'd unravel this a little actually more? I am sure the city would not be offline because of a holiday, but the terrorists report of their great accomplishment might be blunted by fewer body bags.