The complexity of my game selection is what keeps me in business and protects me from big box retailers. Big box may poach the top sellers in any category, but it's the sheer diversity of games available that keeps a game store in business, along with added value in knowledge and game space. I sell over 10,000 individual items in about a dozen departments; as much diversity (but not depth) as Costco. So you would think that additional diversity would be a good thing, especially in a category like Dungeons & Dragons, which I probably know better than any other. Unfortunately, that's not necessarily the case.
Role playing games are spread too thin among too many players who can buy products from too many sources along too long a time line. It's a gigantic pie that can barely sustain any one baker. Worse, it's a collaborative game, so everyone in your game group needs to be eating the same flavor of pie to enjoy it. The diversity is staggering. You can buy RPGs from me, from the 66% of local brick & mortar stores that aren't game stores, from the dreaded Amazon.com, that makes their money from marketing and gives books away for practically free, from 0ther online retailers, or directly from the publisher. You can buy current, in print books, or you can buy a PDF or used copy of virtually any RPG ever printed. This play any book at any time in history is the "long tail" of the RPG industry, a process that divides the RPG pie so thin, that sales of RPGs can be phenomenal, but the lack of critical mass in any one game makes finding a group to play it nearly impossible.
Enter open source gaming, the D20 license, the OGL license, or potentially the GSL license for 4th Edition D&D. Here we take the most popular RPG, Dungeons & Dragons, and fragment it further. D&D has about 50% of the RPG market share in my store, while all D20/OGL product comprises a mere 10%, about what we have for games like Shadowrun or Mutants & Masterminds. Diversity is what keeps Barnes & Noble and Wal-Mart from beating me at my own game, but is it worth it for me to chase these small numbers? The question of the value of open gaming looms larger when you look at our clearance RPG section, of which 40% is D20 product, worth about $50,000 to someone at some point, at full cover price, while now it's not worth the effort to carry it out to the recycling. It's RPG road kill.
I'm actually ambivalent over whether open gaming is helpful or a hindrance to retail. I sure wouldn't want to lose 10% of my RPG sales. At the same time, I think if the open gaming market evaporated, I would see either more Wizards of the Coast D&D sales, or better yet, those people who can't find open gaming options they enjoy, like the various OGL settings (Conan, Arcana Unearthed, etc.), might try another game system. I certainly appreciate diversity in my inventory, it's my security blanket, but when the market spreads itself too thin, a contraction is only natural.