How niche-y can you get?

Crooked Letter Brewing Co. in Ocean Springs, Miss., recently
struck an exclusivity deal with the local casino-resort.

The craft brew revolution has relied, to some extent, on the brewpub for sustainability. This makes sense, beer and food go together naturally. When done correctly, well, and efficiently, the profit margins are significant, but never sufficient unto themselves. Brewing often is a grow or die business, and to stay afloat, breweries have to secure tap handles at other facilities as well.
Since tastes can be fickle--distributors can change their emphasis, a new bartender might push one beer over another-- selling beer to other restaurateurs almost is a full time job in itself. Breweries have "tap takeovers" where they get to showcase their beer (often in exchange for profits in the form of discounts).
The brewer, or brewery representative spends the night at a bar, selling the hell out of all their brands in hopes of a bell-curve bump. It works often enough that breweries continue to do it.
Over the last several years, two new trends have emerged. Breweries increasingly have been partnering with other breweries to create limited-release beers, hoping to increase one another's markets among the beer-faithful. The second, really interesting trend is exclusive recipes. Brew pub brewers developed menu-specific beers for their own foods forever. But now they're forming partnerships with restaurants.
By creating beers to be exclusively sold in a particular restaurant, brewers are able to secure a tap handle, and all but guarantee that the beer is recommended above all others. It's a way for restaurants and brewers alike to create another kind of exclusivity, in a market where rarity is a close second to quality when it comes to specialty beers.
It is nearly paradoxical to talk about how widespread exclusivity is, but there you have it. For people who talk about the craft beer bubble, this is precisely the concern, the divide between becoming Budweiser or continuing to create and fill niche markets. On the surface, it seems breweries must choose. But that model is fewer than 100 years old.
Place-exclusive beers have been the norm for most of human history. Any craft enthusiast will remind you that we haven't nearly the number of breweries as existed before prohibition. As the taste for them goes forward, we may reasonably expect to ask for the house beer at any independent restaurant and not be disappointed.