Jarhead said:i know for the un-disciplined, gun ownership is a great temptation....
I see this as the key issue in a practical sense. Until such time as society is mature enough to trust virtually everyone with personal firearms then the debate is moot.
I think the problem with any licensing system required would be assessing the suitability of people in a stress situation. Almost everyone who posts here has some familiarity with small arms, some have experience limited to standard ranges, others have used close quarters and FIBUA facilities and recognise how easily mistakes, or poor judgement can lead to the death or injury of un-involved parties.
Retaining the level of judgement required to safely use a firearm in self defence in an area where others are present is quite a commitment, and I'd suggest that it's unlikely that all those who would end up carrying would maintain that commitment.