It obviously depends on your definition of carry-on baggage. The regulations are a joke & very often ignored. I've seen people struggling with almost everything you can think of, including the proverbial kitchen sink. Some of these objects are obviously not required on the flight . They cannot possibly be stowed safely in the overhead lockers which is therefore a potential risk to other passengers & crew.
It amazes me what the travelling public thinks of as essentials that they cannot possibly live without for a few hours. I'm told it's even worse on internal flights in the US. Even without the security risk I think it's about time they had a re-think on what is allowed in the passenger cabin of an aircraft.
Ah, ok. You seem like the kind of person who would balk at security measures that seemed excessively extreme, such as forbidding all carry-on luggage. In the wake of the recent threat, banning carry-on luggage (temporarily) is 100% called for, but I feel banning it permanently is a ridiculous and unnecessary inconvenience. You made it sound as though you support a permanent ban-do you?