To expand the thread a little, not sure if this is common in Europe but here's the latest Loco development in these parts.
Jetstar is the loco arm of Qantas. They now have a scheme where they weigh all cabin baggage at the gate. It's a beautiful 2 person routine. Person 1 goes with mobile scales along the boarding line and weighs cabin baggage. Anything over 7kgs the passenger is told - "go see the gate agent over there, you'll need to check that bag in" Then the passenger wanders nonchalantly to the gate agent who writes out a baggage tag and then says, that will be 60 dollars please - about 30 quid. Here's where the fun starts as dismay creeps in across the passenger's face. "But I checked a bag in already" - "Too bad - you should have put all of your excess stuff in there" Last person I saw this week said it was nothing short of daylight robbery to which the gate agent suggested he should find another airline to fly with.
I get why this is done and in many ways support it. I've been dismayed at the growing number of passengers who bring on board a 20 kgs wheelie bag, plus a computer case, plus a massive handbag overflowing with all kinds of stuff. But the way it's been done with this airline leaves a bit to be desired. Yes the website says limit your cabin bag to 7kgs, if you buy checked in baggage at the airport it will cost you big time - but for a long time it was never enforced or policed. It's the change which has caught people on the hop and I wonder how many people will vote with their feet. If not already, how long before the legacy carriers emulate this revenue earning scheme ??