I agree with stricter enforcement of carry-on rules. And (although this is no doubt unenforceable) I think that anyone who brings on more than one carry-on should have to put one bag under the seat in front of them. i.e. only one bag goes into the overhead.
I recently watched one jerk go up and down the aisle, opening every bin, trying to find a place for his second carry-on. His larger one had already been stowed. The FA told him to put his second, smaller bag under the seat in front of him. He refused, and kept trying to force it into the already-full bins.
I could see that the space under the seat in front of him was empty; he was just being a jerk. Everyone else was ready to go. He was of average build, so had no obvious need for extra leg room.
It made me wish that the small, female FA was armed with a cattle prod to make El Jerko do what she told him to do. ARGH!!!
Well now I've had my little tantrum.