Even though I live in Sydney, I buy quite a few things from Amazon.com.
One reason is that I live about forty-five minutes to an hour north of Sydney proper, in the North Shore suburbs, and there are no local gaming stores, friendly or otherwise. There is a Borders in Macquarie Center at North Ryde, and their prices are comparable to a local gaming store, but that's not saying much - prices in Australia do not fluctuate with the weakening of the U.S. dollar and the relative strengthening of our own currency. So I can either make a short drive to Borders, or a very long drive to an actual gaming store, but either way I pay high prices. As it happens, the cheapest of the three gaming stores in Sydney is also run by scumbags, so I won't shop there.
Prime example: Monster Manual IV costs US$34.95 retail. That's about A$46.95. Napoleon's Military Bookshop, the gaming store I used to go to because my friend worked there, is presently advertising it on their website for A$60. With Amazon standard international shipping to my home in Sydney, I can get the damn thing for US$34.00, or about A$45. I just don't see the sense in buying from a local store - even if I could get the book shipped free by Napoleon's (which I can't), much less when you consider the incredibly high cost of petrol (Americans have nothing to complain about, trust me) for the two-hour roundtrip and the cost of parking even at cheap city rates on a weekend.
I can go to Borders, sure, it's only a fifteen-minute drive away, but I'm still going to pay high-ish prices, and at that point I'm not supporting a local gaming store - I'm supporting a huge foreign corporation, just like Amazon. Not that Napoleon's Military Bookshop is a gaming store in the "community resource" sense, and the other store I would shop at - The Tin Soldier - is only just beginning to consider things like hosting gaming.
The other reason I shop through Amazon is that my fiancee lives in California, and we visit each other regularly - so I can skip the extra cost of international mail and get everything sent to her apartment on free Super-Saver shipping, and just get one or the other of us to bring it to Sydney.
If the games I wanted weren't available through Amazon, I would turn to PDF purchases more often - I already own a few True20 products on PDF, for instance, because I don't care about having a hardcopy of those games enough to even go through Amazon, much less a more expensive or less-convenient option. There are quite a few Wizards of the Coast books I would be content to own on PDF, though not at the full price and not from DriveThru RPG in any case until they start accepting American Express.