9/11. It needs no year, no further explanation.

But the instant recognition and raw power of that phrase has made it easy for that terrible event to slide into pop culture. Eight years later, the World Trade Center is still a hole in the ground, but now surrounded by souvenir sellers with 9/11 T-shirts and knick-knacks.

One problem with rebuilding on the site is that, in these times of recession, there isn't enough commercial demand for the new buildings that would replace the World Trade towers. Spending billions to say "You can't beat us" to terrorists seems foolish to many if the buildings will sit empty.