Janis Joplin: You only have to do one thing well to make it in this world.

Janis said it, but it true for baking?

Are there any successful bakeries that do just one thing well?

What about 1 thing well/month, like Olive Bread in May, 60% Caraway Rye in June, etc.?

I believe makes only one kind of bread and is successful at it. Read about him here on MC Farine's blog http://www.farine-mc.com/2009/11/meet-baker-gerard-rubaud.html

One must always, however, keep in mind the many definitions of "success."