I'm long haul cabin crew for an airline that serves free alcohol. In my 20 years flying I can really only recall a handful of incidents.
Through training and experience we're quite good at nipping any potentially nasty alcohol related situations in the bud.
We are aware of how much each passenger has had and if we think they are getting drunk we have discreet ways of getting them to slow down.
Each situation is judged individually and it's our call whether we decide to point blank refuse to serve them anymore, although this actually can cause more problems and cause the passenger to become defensive or abusive.
I actually hate refusing anyone drink...its not coming out of my pocket and I want everyone's holiday to get of to a nice start.
I do find most people do know their limits and really just want to enjoy a glass of wine with their meal.
Funny...I've just realised that of the few incidents I have had they were either people drinking their own alcohol (purchased beforehand in the duty free ) or people who have taken medication, say sleeping tablets, and then had a drink.
Maybe I've been lucky, maybe it's because I work for a large scheduled airline where we don't tend to have large groups of stags etc but in my experience the vast majority of people drink very responsibly on board and behave very well.
I therefore would see no reason for a ban.