Amazon.com continues to set the bar for online commerce and community. Not content to remain simply "the world's largest bookstore," they have expanded their inventory over the years to include Music, Kitchen & Housewares, Apparel & Accessories, Electronics, Shoes, Health & Personal Care, and more. And despite growing to immense proportions, they've managed to avoid the criticism that other online plays have faced in their attempts to diversify (e.g., Google).
Amazon is perhaps best know for being a pioneer in collaborative filtering ("Customers who bought this also bought..."). While many companies talked about using this type of technology for cross-sell and up-sell opportunities, few have implemented it so successfully. In fact, Amazon is usually referenced in conversations about collaborative filtering, as it's the best known example of it in practice.
But Amazon didn't stop there. Long before consumer generated media became a buzzword, they encouraged users to post product reviews, build and share Wish Lists, and traverse Purchase Circles. They created the foundation for what Tim O'Reilly calls an "architecture of participation," or, the basis for Web 2.0.
With the introduction of its Amazon Connect author blogs and product wikis, Amazon has now fully embraced the principles of Web 2.0, and they've done so in a manner that is relevant to their customers, suppliers, partners, and products. They've been able to maintain an extremely intuitive and useful site experience, while others still struggle with how - or even when - to introduce such features and functionality (read this great article about companies that are doomed to fail, due to an inability to systematically change the way they do business).
That is why I will continue to buy from Amazon, when links to BarnesandNoble.com, BestBuy.com and other successful retailers are just one click away. I've had a long and happy relationship with this one site, that will only get better over time.