Social Capital: A Discussion Paper [pdf] (by the Cabinet Office, part of UK government) covers the concept of social capital, as popularised by Robert Putnam. There are four main topics covered: what social capital is and why it matters; what evidence there is and what the consequences are; the future trends of social capital in the UK; what the government can do to influence this. It's short (ish) and easy to read. And there's a brilliant graph in the introduction: The Exponential Growth in References to Social Capital in the Academic Literature, 1985-2000.

And later in the paper, when discussing possible ideas to stimulate social capital, there's this (paragraph 169): "Mobile telephones could have emergency help keys or codes that would activate the nearest five phones to indicate the holder is in trouble and needs assistance".

See also: my notes on the Cabinet Office document; another review of Social Capital: A Discussion Paper.