Guns, I hate to break it to you, but online retailers DO harm the brick and mortar stores, and not just the mom-and-pop shops. Netflix killed Blockbuster, hunted it down until there was nothing left. Amazon killed Borders, and has Barnes and Noble on the ropes. These aren't small names we're talking about here.
Reno also brings up a good point. The FLGS is typically the 'point of entry' into different games and genres for new players. Sure, someone who knows they want D&D books can find them easily online. But you can't survive off just marketing to current consumers. Some will leave the hobby due to age, money, lack of group, etc. If you don't replace them (or preferably increase your numbers) with new consumers, then you're dead already, and you don't even know it. And the FLGS is where the majority of new consumers come from. Especially if they, say, go in to see what new Warhammer minis are available, and while they're browsing, they find this book called Shadowrun, like the art, and take a look. Or they go in for the Pathfinder book they ordered, and spot All Flesh Must Be Eaten out of the corner of their eye. That is the entire reason brick and mortar stores put products on display, afterall. People who come in for one thing might stop, see the shiny, and buy that too. It is all interconnected like a spiderweb.
Amazon, however, is much more restricted in this sense. Sure, you can browse through the endless screens of line by line product entries, but a one inch picture of the cover of a book (if that) isn't going to excite you like running your finger along a bookshelf and finding an interesting title. Even when you click on the thing you were looking for, if there are product suggestions, they're all different things in the same product line for the most part. You don't get the cross-pollination you see in the brick and mortar store. And the game industry as a whole suffers for this. Sure, games like D&D, Pathfinder, WoD, and Shadowrun will be fine, for the most part. They're the big dogs in this fight, afterall. But the smaller games, like the Serenity RPG, or ParanoiaXP, or Big Eyes Small Mouth are put at risk, because they just don't have the exposure. And the smallest games go out altogether, never having had a chance. A similar situation exists in news media today. You know how pretty much all news coverage in the US boils down to about 3-4 points of view? That's because the vast majority of newspapers, news radio, and cable news providers are owned by a handful of companies.
"But what about word of mouth online?" you say. "Why can't companies use social media to promote themselves?" Simply put, the signal to noise ratio is too damn high. Anything worthwhile gets drowned out by the hordes of cat .gifs, homophobic rants, porn, and more. Have you TRIED looking through random Twitter or Facebook posts? Either you restrict the flow of information you listen to so that it is an echo chamber, with everyone rubbing one out to how great their hobby is, or you are drowned in a sea of information that makes the Pacific look like a drop in the bucket.
