Imagine you are in the market for a new car.
Under normal circumstances, you arrive at the dealership, and browse a few models until you settle on the one with all the features you desire. You negotiate with the salesman, end up buying it, and drive off the lot. All the features, from the power windows, brakes, radio, etc. work as expected, and you're happy with your investment as you cruise in your new wheels.
You have entered the Twilight Zone
Now, imagine a different set of experiences. Rewind the story back to the dealership. Once settling on the car possessing all the features you desire, you negotiate with the salesman. Before settling on a price, the salesman warns you that once purchased, all the car's wonderful features that you fell in love with will only function if 1000 other individuals also buy this same model car. Otherwise, your new car won't even drive off the lot.
Ready to sign on the dotted line? My guess is you'll likely hesitate since the fulfillment of your investment relies upon many other people buying the same vehicle. That is the catch-22 of building online community: It does not work if no one else participates, and most people refuse to participate if it's not already working.
Making things worse, there are hundreds of other car dealers in the area, and once the customer walks out the door, he's probably not coming back, even if enough people magically purchase the threshold quantity to make the vehicle work. There's just too much competition for the customer's attention.
A challenge of community building is providing value and attracting the right new members while in the fledgling state. Perhaps more art than science, the initial work of the community leader is to create value in the very beginning - value that need not require a mature community to even exist yet. That value exchange is not cast in stone, and as the community grows, the methods use to create value may need change.