Even Facebook doesn't have demographics and user info. on all of its users, as this ReadWriteWeb story illustrates. In particular, look at the comments which point out all of the problems with using an incomplete set of data.
Facebook doesn't require users to provide age, geographic location and other basic demographic data when they sign up. Thus, the user data you get when you go through the self-serve advertising program doesn't include all of those people who didn't submit data. And you don't know how many, or how these missing people differ.
Also, Facebook doesn't require people to update their data, which causes other problems. One of the ReadWriteWeb story commenters noted that students who graduate from a high school or college may or may not be counted as students.
Facebook data should not be used for planning your social media strategies and services. You're better off guessing than using this data. Bad data may
mislead you into targeting the wrong audience or putting emphasis on the wrong features.
If you guess, you know it's a guess. And you'll proceed more cautiously, perhaps do more testing, and plan your limited resources more conservatively until you can get real key performance indicators.
Facebook's user data is only good if you want to:
- buying Facebook advertising to reach Facebook users, and
- you know that you're only getting some unknown percent of your target audience, so you've planned other ways to reach them.