I got my bags searched and an item confiscated a couple of weeks ago, on a flight to Amsterdam. The item in question had cleared security many times before (and was in no way dangerous, but one of course has no right of appeal - attempting to disagree is very counterproductive. I could easily have been banned from flying, and then - hey - I'd be in the same boat (but not plane) as the people in this incident). You lose a lot of what one might otherwise imagine are basic human rights when going through security -- dignity, the right of property and of ordinary justice can be suspended on a whim. But that's another thread!
I'd forgotten my gizmo was there. It was just rattling around at the bottom of a holdall that I often use to carry a mixture of electronic stuff and small tools around. Doubtless the things that were confiscated this time were real knives, but that doesn't mean they were intended for use on voyage.
I don't, as a rule, use or carry knives. Many of my friends -- especially those who live and work in the Scandinavian countryside -- do, to the point (ahem) at which they are as unremarkable as ballpoint pens. Do you know which pens, how many pens or even whether you have a pen in your jacket at the moment?
I would suggest that on the balance of probabilities, the knife carriers have as much to do with terrorism as they do with the 1968 Portuguese entry in the Eurovision Song Contest. Yes, you should always know exactly what you're carrying around when you board a plane, but with flying in Europe increasingly part of everyday life it's human nature to lose the details in the clutter of normal business.
R