It is an inevitability that the industry will be taken over by giant corporations. However, this doesn't necessarily spell the end for small boutique places. I 100% agree with @SynapSemilia that the only way we can truly vote these days are with our dollars. If you don't shop at Walmart, you probably won't buy your bud from the Walmart of cannabis. In my mind, legalization is the top priority, after that we can worry about big companies taking their slice; but make no mistake, they will take their slice, and keeping marijuana illegal for fear of it being co-opted is nonsense. I'm no fan of big business and their practices, but they aren't decapitating and hanging civilians in the street for refusing to work with them.
In many areas, the focus is moving away from large companies to small ones, and I think the younger generations have caught on to the fact that cheaper is not better. Whether it's farm to table food or artisan furniture, there is now more than ever before an opportunity for small businesses to make their impact on the market if they offer a truly unique and solid product. While their profits will never ever ever come close to that of big corporations, it is entirely possible for small local shops to thrive if they offer a great product or a unique service and can foster a sense of pride in their community.