The introduction, which is what I've read so far, tells a tale about a guy who because of the numerous and deep face to face relationships found a donar kidney from a stranger following his contracting of a genetically inherited kidney disease, otherwise he would have been dead, the book says that there is a statistical chance of 1 in 3000 that you will have a stranger volunteer to give you a kidney, he had four seperate offers.
Although that is a kind of exchange theory thing and the author says that they were going to elaborate on social neuroscience and it found that so called "frivolous" contact, such as meeting for coffee once a week or to play cards, was likely to increase your longevity as much as taking beta blockers or giving up smoking, which seems pretty major.
My brother talked to me this morning though about some tensions between him and his friends arising from invites to social gatherings and attempts to get people to come out and socialise resulting in last minute cancellations and frustrations like that, which I guess could be a down side, I've not read yet much about the quality of the social face to face interaction as opposed to the interaction happening per se.
Which is something that I reflect on quite a lot during my more extrovert phases, I may want to have more face to face contact or socialise more but in the general run of things, particularly given my home town, there are a lot of very significant barriers and obstacles to the same, ie intelligence, social background, community background and the like.