Regular readers know two of my prejudices:
1. Skepticism about the power of social media.
2. The importance of marketing to the heavy user in a category.
Unless you are competing in a high interest category (entertainment, sports, wine, etc.) the idea that people are going to find online social interest in your brand is likely to be an expensive pipe dream.
The stuff that most of us sell -- motor oil, peanut butter, socks, and insurance -- is probably not going to play a significant role in the online social life of many people, regardless of what the social media hustlers say.
But there may be a way for brands in low-interest categories to find value in social media.
The answer, once again, is "the heavy user, stupid."
In most categories there are maniacs. The maniacs tend to have unusual interest in the category, unusual knowledge of the category, and unusually high spending in the category. These people are also unusually influential. We all know someone who's an audio maniac, for example, and when it's time to buy headphones we ask him what to buy.
A smart social media strategy may be to determine what it is about the category that motivates and interests these unusual people, and build a social strategy around that, rather than the product itself.
Don't worry about how many members/visitors/contributors your effort is reaching. Just make sure you're reaching the maniacs.