I've just been sent, and filled in, a survey by Merrill Lynch on social networking. As a reward I got to see the results of the survey so far. Unfortunately I have no idea how the sample was selected. You might like to try it, too. Here is the url.
It reached me (indirectly) via Thomas Power of Ecademy, the business networking site. Presumably, as someone running a subscription model, Thomas was interested in and possibly alarmed by the results for question 31: "How much would you pay to access a social networking site? 75% said they wouldn't pay, the next largest group saying £1-3 per month.
Respondents seem to see social networking as being here for the long term, though: 84% expected still to be using social networking sites in 5 years time and, in the case of 64%, even in 10 years time. If a week is a long time in politics, how long is 10 years on the Web?