Launching an exclusive community can be a great idea.
You can target and attract a specific group of people. You can generate an extremely strong sense of community amongst a group of people with a VERY strong common interest. You can build a community that delivers an incredible ROI.
It's also an effective positioning tool. When there are established communities for that topic, your new community stands out.
But, as obvious as it sounds, exclusive communities need to be exclusive. That means they're smaller, much smaller. That's the sacrifice. It has to be difficult to join. You have to have a criteria that members meet. You can't make exceptions for anyone (let alone everyone).
It also has to make sense within the topic. It makes no sense, for example, for a community about salads to be exclusive. It does make sense for professionals.
And if you're going to build an exclusive community, try to avoid sentences like this:
And the best part is that membership in this private club is free and open to anyone with a salad bowl, a pair of tongs and a passion for the green stuff.
You can have a private club or an open club, but you can't have both.