Indeed weight has become an issue. The bag itself being relatively light to the kit inside it of course... the decision on what to pack is really the key factor. Have only had cabin baggage weighed once, by Ryanair in France, they weighed every bag for every one, not a hope of making it look light.
Another incident, I remembered I had a small hunting knife in my jacket pocket in Nice, I remembered this at check-in, popped it in my check-in bag before handing it over. I turned around with my boarding card to see an armed soldier right behind me. He followed me all the way to the gate, an hour and a half later. Not the most relaxing time I've had at an airport.