Yesterday in the Wall Street Journal, there was an article by By Huaxia Rui, Andrew Whinston and Elizabeth Winkler on how businesses can use Twitter to predict sales. You can read the article at http://tinyurl.com/yftyoqs.

They use the example of three movies on which they tracked Tweets. They imply a correlation between the number of positive Tweets and ticket sales for the movies and write:

“Social-media sites such as Twitter have made it increasingly easy to find out what consumers think and want without the limitations and bias associated with older market-research tools such as surveys and focus groups.”

I agree with this statement. But I have a major reservation with it as well.

The only people whose opinions you hear on Twitter are those who Tweet. You don’t even get all the people who are on Twitter, let alone all those who are not. The same is true for any other social medium. You only hear from those who speak about that topic through that social medium.

For some categories, such as movies, there may be a relationship between positive Tweets and ticket sales. This may also be true for other categories that have to do with how people spend their leisure time.

But aggregate information from people who Tweet on a given topic can really only give you reliable information on people who Tweet on that topic. If they are the entire stakeholder group you care about, you’re golden. But more often than not, they will not be a representative sample of the population you wish to know about.

So, marketer beware!