It's hard to believe that we're that good or that lucky.

That suggests some possibilities:

1. The threat was overstated.*
2. We've hurt them more than we know.
3. Something is in the works and they're hoarding their resources.

In things like this, it pays to be a pessimist and go with option 3. Years ago, I heard a statement attributed (probably falsely) to Ben Franklin. It went something like this:

"Some people are optimists. They go through life hoping for the best and are frequently disappointed. I, on the other hand, am a pessimist. I go through life expecting the worse. If something bad happens, I'm prepared for it. On the other hand, if nothing happens, then I'm pleasantly surprised."

The closest thing I can recall to a terrorist attack since 9-11 was a lone gunman shooting up a line of people standing in an El Al ticket counter at LAX. It was on July 4, 2002 and he killed 3 people.

*On the other hand, they've no doubt learned they can inflict untold millions of dollars of economic damages with nothing more than "chatter" on their websites. For virtually no cost or risk, they can easily cause us to spend tons of money in increased security while scaring people from going out and living their lives.