If the Boston Beer Company kicks it up to 2.5 million barrels, is it no longer a craft brewer? Can a macro brewer ever mimic a craft brewer closely enough to call its product a craft beer? Is size the only determinant of quality?

The craft community is split. On the one hand, since when is size a bad thing? "The size of a brewery has nothing to do with the quality of the beer being produced inside of it," wrote one commenter on beeradvocate.com. "Good beer can be produced on a large scale." Added another: "Not only can it be done, but I'm sure it can be done a lot easier." By many reports, AC Golden is run by just a handful of brewers, largely cut off from the MillerCoors mothership. So it's all good, right?

Not everyone agrees. There's no question about why MillerCoors wants a cut of the craft beer market—although overall beer sales were down 2.2 percent in 2009, its worst performance in years, the craft market was up 10 percent. But there's a deeper question involved. "Craft beer being produced inside a macro brewery is the equivalent to health food being produced at McDonald's," wrote one poster. It's almost spiritual criticism: Even if the beer is good now, the corporate values (or lack thereof) inherent in MillerCoors's control will destroy the soul, if not the quality, of the beer.

Craft brewers themselves are likewise divided. Over the last year I've chatted with dozens about the craft-ification of Big Beer. Some say it's a matter of rising tides: if MillerCoors uses its economic power to convince Joe Sixpack to buy better beer, then some of those Joes will venture farther afield. Others celebrate the fact that they have had enough of an impact on the market to force the big brewers to step up their game.

Craft brewers aren't stupid—the best, at least, are at least at good at selling their wares as making them. But with 10 percent annual growth and the overhang of a "movement" identity still shaping the sector's ethos, there's still a naiveté about what kind of heat the likes of MillerCoors can bring. According to AC Golden, Colorado Native Lager was in 600 stores just six weeks after its release, placed alongside Avery, Great Divide, and other Colorado microbrews. Nothing on the label identifies it as a MillerCoors product. As long as 10 percent growth is the rule, there might be room for corporate pretenders. But that growth will top off at some point, and craft brewers will suddenly find themselves struggling for shelf space, even in their own niche market, with the mega-brewers. True small-timers may have a superior product, but are they ready for this fight?