I do think people overestimate the actual impact of "going viral". The question is staying power: something else will be viral next week, and today's sensation will be gone. How many people will remember "Get Kony 2012" at the end of the year?

Reaching a million or ten million or 100 million eyeballs doesn't mean much if the only action taken at the other end is a click on "like" or "share" and the material is forgotten within hours or minutes.

I'd think building a small but committed network that stays together and keeps coming back is a more effective use of social media than generating a viral sensation that's here today and long gone tomorrow.