Hi Klaatu. Great show and very thought provoking. 

You missed one type of friendship that applies to me and, I dare say, many others.

I grew up and went to school in London and became one of a group of 7 "mates". We never used the term "friends" in case we were deemed "soft" - crazy I know. Over the years we have all moved away from each other, in one case to the other side of the world, so we often only meet one another once or twice a year, sometimes not even that, and don't even converse by phone or messaging much in between. Despite that we all know that we can totally rely on one another should the need arise, and when we do meet the intervening months or years simply have no relevance.

Apart from my immediate family, of course, these people are closer to me than anybody else but the need to be in constant contact just doesn't exist. It's the polar opposite of people who are constantly on Facebook communicating with "friends" they've never met, and really know nothing about with any certainty.