FB may personalize weighting component of EdgeRank differently for different fans. Eg, some fans prefer text over photos, and others prefer photos over text. Unlikely, but possible.
When you first launch the page, you expect a certain demographic based on your other marketing efforts. You might buy ads targeted at this “ideal customer" demographic. Over the next few months, you expect the demographic composition of your Total fans to reflect the “ideal customer." And if everything works according to plan you can expect the demographic composition of the people who see your content and the people who engage with your content (the "talkers") to reflect both the “ideal customes" and the “fans."
If that happens to you, it’s time to start figuring out the root cause for why these groups diverged:we either don’t understand who our customers are or we have a (potentially flawed) Facebook marketing strategy that only reaches a segment of our customers. For example, the community manager may be niching their status updates too tightly or just posting stuff that they “personally find interesting.”If we have wrong expectations about our customers, we need to reposition all our marketing--not just Facebook--to more effectively reach the new "target market".