The carry on baggage issue was aired in the New Zealand Herald recently by the travel columnist. It was a very very good article. Take a look here
Jim Eagles: Do carry-on bag hogs get you riled? - Travel - NZ Herald News
There was a follow up article here
Jim Eagles: Angry readers react to overhead locker hogs - Travel - NZ Herald News
I particularly liked this bit of the second article
If that doesn't sound very encouraging, Thomas AB suggested a tactic frustrated passengers could adopt.
"Whenever I go to my seat and my overhead locker is full, which happens often, I take out some luggage and put it on the floor. If someone from another row claims it, I pass it on to them to store above their row. Most of the time the stewardess intervenes and takes away their luggage to store it somewhere else. Works for me."