I pretty much agree that there will not be another attack in the style of the events of September 11th (I don't like the catch-all term "9/11", I think it's degrading to the scale of the event and the people involved). But never say never.
However, the measures and, the importantly, the mentality are in place to help prevent such a thing from happening again. But, as we are all aware I'm sure, there are gaps. In commercial and general aviation, and even more so in other segments of our society, there are still gaps that I'm sure the bad guys will try to exploit. Never forget what happened, always be suspicious, and don't worry about hurting anyone's feelings (ie, I'm all for profiling).
And I don't think it's a stupid question all at. Regardless of the original poster's background or experience, it's a perfectly legitimate question deserving discussion (even if it probably has been been discussed ad nauseum in the last couple of years), so long as the discussion doesn't of course reveal any information not appropriate for a public forum.