It occurred to me yesterday that there is a different approach to social networks, which is potentially even more important - but has been utterly neglected by an industry still besotted with mass audiences and reach.
Rather than using network effects to reach a lot of people indiscriminately and cheaply, it uses network effects to reach very few people precisely and expensively. And rather than outsourcing media buying to the public, it works by outsourcing media planning to the public.
I'll give you an example of how this might work. Let's say you and your wife/mistress/boyfriend/husband/sheep have just spent a lovely weekend in a hotel in the Cotswolds. You get home and receive a thank-you letter or e-mail from the hotel. And inside is a voucher for "three nights for the price of one" at the hotel. It's not for you, but it's to give to any one person you choose.
You mentally scan your address list of perhaps 50 to 100 people and choose the one person who would most enjoy The Upitsownarse Arms in Upper Slaughter. In making this choice, you factor in taste, wealth, age, geographical location, marital status, size of household etc.
Now, the amount of intelligence which is applied in that act of individual selection simply surpasses any level of targeting you could achieve through databases or other automated means.