Mr. __________ or Mr. Bob???

So a couple of people and I were discussing the other day about how kids in our society today seem to be more disrepectful to their authority. When I was little I use to call other adults Mr. and Mrs. Last Name. But, when I got older I started saying Mr. Bob or Ms. Kathy. So, when our kids were born there were people that were so familiar to them that it just seemed to formal to do the last name thing, so we started going by Mr. First Name or Ms. First Name. No one has really said anything about it, although on occasion I will get an adult who corrects even me and asks me to have the kids call them by their last name with the appropriate prefix. But, in our conversation it came up about kids even calling adults just by their first name alone. Could this be one of the reasons there is such a lack of respect toward those in authority??? My thought is that the prefix in front shows the respect needed and the first name shows familiarity. Just curious what your thought is on the situation??? Or are the different situations that call for different titles (outside Doctors and dentists)??? What do you think?