At Paul's prompting, I've been stupid enough to sign up for Facebook, which reveals that I have precisely two friends. I'm so lonesome I could cry.
But lonesomeness isn't just a social problem. It's an economic problem. There are strong reasons to think friendship can improve economic growth, through (at least) three channels:
1. Friendship builds trust, and trust can increase economic activity in several ways.
a) It can overcome the market for lemons problem. If you don't know any builders, you might not want to employ any, for fear of getting a cowboy. But if you or a friend knows one, you might employ him.
b) If everyone distrusts others, they'll invest in either rent-seeking or rent-protecting activities - such as security guards and CCTV. If they do trust others, they're more likely to invest in socially productive activity, as the fear of predation is diminished.
c) Social networks can police informal contracts based on the "invisible handshake" (pdf). One reason why the City first became a powerful financial centre was that transactions were based upon trust - "a gentleman's word is his bond." But this worked not because men were naturally honest, but because if they failed to be so, the sanctions were harsh. Word of one's dishonesty would quickly spread, causing one to lose friends and livelihood.
2. Social networks can improve productivity by improving the match between workers and jobs, as Emilio Castilla has shown. They can also improve workers' productivity by increasing their skills, simply because people chat in pubs and bars. Work by Mark Granovetter, such as this pdf, shows that these mechanisms may account for some of the success of Silicon Valley.
3. Networks can help convert ideas into entrepreneurship. The problem here is that there's a "knowledge filter" - there are many barriers between having a good idea and having a company that turns that idea into money. Networks can help break through these barriers. For example, they help inventors or researchers meet salesman. And they are better ways of communicating semi-tacit knowledge. A chat over a drink can convert a vague idea into something more concrete and useable.
Now, things aren't as simple as I've made out. Some think networking can raise unemployment, and that some types of network can cut growth (pdf); there's much more here.
Nevertheless, it is possible that a friendlier society means a richer economy. Hank Williams might have made a fortune from being lonesome, but mere mortals can't.