I've mulled this one over many a home-brew, and I realized after not too long that the part that was the most fun, interesting, and exciting thing about home-brewing was creating. Sadly, as a brewery, your going to be doing 95% production, marketing, sales, and paperwork and 5% creative work with the beer (if your lucky and do lots of risky seasonal and short run brews).
Oh sure, it would be a "dream" once it was the size of Sam Adams or New Belgium and there was enough business to support the crazy owner's wacky ideas.
If I ever do turn this hobby into a business, I will likely stick closer to my wheel-house with a retail shop. And to the nay-sayers, it is possible to run a brick and mortar just as profitably as an online shop. You have higher overhead, but generally better convenience, as your product is available right now (which is handy when you realize that in all that playing with the recipe and adding and removing of things from your cart...you never added back the yeast...).
Also, you might be shocked to learn how many LHBSs get regular shipments from places like MoreBeer. Its faster for them, the prices are likely only 10-15% higher than their normal supplier (for some things like grains), and there is no minimum order. If your not going to move 55lbs of Belgian Special B in a year, it certainly doesnt make sense to be buying it in such large lots...especially when a maltster is going to want to know how many sacks you want (and 1 is a silly answer).
Everyone is cost conscious today, but people still do pay for convenience, whether its $10 for two day air or an extra $5 at a LHBS.