What IS permitted then? Common sense tells me that most people who habitually carry a handbag, and have it at their feet will grab it on the way out. These handbags range in size from quite small to ... I suspect some here will say these too should be left behind, but I cannot see that as being very likely.
Is this dangerous? Depending on the size of the bag, probably not.
I have a small 'man-bag' that has my medicine, glucose metre and test strips, my money, my iPad and my documents. It never goes in the overhead bin and it is smaller than my wife's handbag. I can assure you that I will be taking this with me in any evacuation.
This theme repeats here from time to time, usually after an evacuation where youtube videos show the 'morons'. However, like some others here, I cannot recall any incident which was made worse by the 'morons'. Intuitively it feels right that carry-on should be left behind, but this isn't supported by the facts.
I think this safety rule should be re-looked into by the regulators. The rule has been in place for many, many years and it is taken as gospel that it is right to have it - although it cannot be enforced. But perhaps a variation would be more effective. If the rule stated that nothing other than a small 'personal' item (with specific dimensions) can be taken in an evacuation perhaps many of the morons can be encouraged to be better prepared. The baggage industry would love it, they could market all sorts of products to suit the new rule. Of course you will always have 'morons' but give people a rule they can follow and perhaps many will do so.
Oh, and can someone remind me of the airline's liability for loss or damage of items in carry-on? I don't think MC99 liability applies to carry on, but even if it did their liability is capped.