I don't disagree, but there have been cases where I wondered if my support of a local business was actually valued at all by that business. Not film related, necessarily, but here's one example: The Leica Store in San Francisco.
Let's not get into the whole "who's stupid enough to spend the money on a Leica camera?" because the answer is obviously "I am", but I bought my M-A, a lens and a bunch of other stuff from that store and I'm virtually ignored every time I walk in there. And when I do manage to talk to someone they seem completely disinterested in my business. I did bear with it "in support of my local store" (not really that local, as I've pointed out in this thread), but I eventually gave up and starting buying my Leica gear elsewhere. Sure, I'm ordering online now and can't necessarily touch/feel the product before I buy it, but the out-of-state Leica dealer I've been dealing with is a real pleasure and every purchase has been as smooth as silk. As a perk, the store is not obligated to charge CA sales tax on my purchases so I'm saving a bit of money too.
So, while I am generally in agreement that it is good to support local businesses, some simply don't deserve that support.