Part of the reason I blame the free market is because of the timing, but also because many of the functions that used to be performed by the family and community are now performed by businesses.
Specifically, I think the fact that middle-class people in Western countries no longer rely on friends, family and neighbours to meet (or even augment) our material needs has changed the way that we perceive interpersonal relationships on an individual level.
Because most forms of maintaining personal relationships come with real costs (monetary, stress/expectations, time, lost sleep) but minimal tangible benefits outside of the existence of the relationship itself, our "social mammal mental accounting software" discounts their value.
The net result is that we engage with friends, family and neighbours just enough to keep the relationship alive, but no more. We're lonelier, sadder and less fulfilled.
It's pretty bleak, and I'll admit it's a pretty broad stretch of logic, but I think it's at least partially true based on both my own experiences and the conversations I've had with the people I'm close to.
I could see that being true. Do you mean businesses like Facebook and Twitter with their substitution for socializing?
I fully agree with the rest of your post. If you're interested in the subject, I would suggest reading Robert Putnam's research on Social Capital. Bowling Alone is a good synthesis (but I'd personally pass on his other books, which lean more toward polemics).
I think this subject is one of the more important ones to the US right now, and is largely ignored because it makes a lot of ideologies look bad. I'd be curious what leads you to your accusation.